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NAME

       barchart -  Bar chart for plotting X-Y coordinate data.

SYNOPSIS

       barchart pathName ?option value?...
_________________________________________________________________

DESCRIPTION

       The  barchart  command  creates  a  bar  chart  for  plotting  two-dimensional  data  (X-Y
       coordinates). A bar chart is a graphic means of comparing numbers by  displaying  bars  of
       lengths  proportional  to the y-coordinates of the points they represented.  The bar chart
       has many configurable components: coordinate axes, elements,  legend,  grid  lines,  cross
       hairs, etc.  They allow you to customize the look and feel of the graph.

INTRODUCTION

       The  barchart  command  creates  a  new  window  for  plotting  two-dimensional  data (X-Y
       coordinates), using bars of various lengths to represent the data points.   The  bars  are
       drawn  in  a  rectangular  area  displayed  in  the center of the new window.  This is the
       plotting area.  The coordinate axes are drawn in  the  margins  surrounding  the  plotting
       area.  By default, the legend is drawn in the right margin.  The title is displayed in top
       margin.

       A barchart widget has several configurable components:  coordinate  axes,  data  elements,
       legend,  grid,  cross hairs, pens, postscript, and annotation markers.  Each component can
       be queried or modified.

       axis

                 Up to four coordinate axes (two X-coordinate and two Y-coordinate axes)  can  be
                 displayed,  but  you  can  create  and use any number of axes. Axes control what
                 region of data is displayed and how the data is scaled. Each  axis  consists  of
                 the  axis  line,  title,  major  and  minor  ticks, and tick labels. Tick labels
                 display the value at each major tick.

       crosshairs
                 Cross hairs are used to position the mouse pointer  relative  to  the  X  and  Y
                 coordinate  axes.  Two perpendicular lines, intersecting at the current location
                 of the mouse, extend across the plotting area to the coordinate axes.

       element   An element represents a set of data to be plotted.   It  contains  an  x  and  y
                 vector  of values representing the data points.  Each data point is displayed as
                 a bar where the length of the bar is proportional to the ordinate (Y-coordinate)
                 of  the  data  point.  The appearance of the bar, such as its color, stipple, or
                 relief is configurable.

                 A special case exists when two or more data points have the  same  abscissa  (X-
                 coordinate).   By default, the bars are overlayed, one on top of the other.  The
                 bars are drawn in the order of the element  display  list.   But  you  can  also
                 configure  the bars to be displayed in two other ways.  They may be displayed as
                 a stack, where each bar (with the same abscissa) is stacked on the previous.  Or
                 they  can  be  drawn  side-by-side  as  thin  bars.   The width of each bar is a
                 function of the number of data points with the same abscissa.

       grid      Extends the major and minor  ticks  of  the  X-axis  and/or  Y-axis  across  the
                 plotting area.

       legend    The legend displays the name and symbol of each data element.  The legend can be
                 drawn in any margin or in the plotting area.

       marker    Markers are used annotate or highlight areas of  the  graph.  For  example,  you
                 could  use  a  text  marker  to  label  a particular data point. Markers come in
                 various forms: text strings, bitmaps, connected line segments, images, polygons,
                 or embedded widgets.

       pen       Pens define attributes for elements.  Data elements use pens to specify how they
                 should be drawn.  A data element may use many pens at once.  Here the particular
                 pen  used  for a data point is determined from each element's weight vector (see
                 the element's -weight and -style options).

       postscript
                 The widget can generate  encapsulated  PostScript  output.  This  component  has
                 several options to configure how the PostScript is generated.

SYNTAX

       barchart  pathName  ?option  value?...  The barchart command creates a new window pathName
       and makes it into a barchart widget.  At the time this command is invoked, there must  not
       exist  a  window named pathName, but pathName's parent must exist.  Additional options may
       be specified on the command line or in the option database to  configure  aspects  of  the
       graph  such  as  its  colors  and  font.   See the configure operation below for the exact
       details about what option and value pairs are valid.

       If successful, barchart returns the path name of the widget.  It also creates  a  new  Tcl
       command  by  the  same  name.   You can use this command to invoke various operations that
       query or modify the graph.   The  general  form  is:  pathName  operation  ?arg?...   Both
       operation  and  its arguments determine the exact behavior of the command.  The operations
       available for the graph are described in the BARCHART OPERATIONS section.

       The command can also be used to  access  components  of  the  graph.   pathName  component
       operation  ?arg?...   The  operation,  now located after the name of the component, is the
       function to be performed on that component. Each component has its own set  of  operations
       that manipulate that component.  They will be described below in their own sections.

EXAMPLE

       The barchart command creates a new bar chart.

              # Create a new bar chart.  Plotting area is black.
              barchart .b -plotbackground black

       A  new  Tcl  command  .b is created.  This command can be used to query and modify the bar
       chart.  For example, to change the title of the graph  to  "My  Plot",  you  use  the  new
       command and the configure operation.

              # Change the title.
              .b configure -title "My Plot"

       To add data elements, you use the command and the element component.

              # Create a new element named "e1"
              .b element create e1 \
                -xdata { 1 2 3 4 5 6 7 8 9 10 } \
                -ydata { 26.18 50.46 72.85 93.31 111.86 128.47 143.14
                   155.85 166.60 175.38 }

       The  element's  X-Y  coordinates  are  specified using lists of numbers.  Alternately, BLT
       vectors could be used to hold the X-Y coordinates.

              # Create two vectors and add them to the barchart.
              vector xVector yVector
              xVector set { 1 2 3 4 5 6 7 8 9 10 }
              yVector set { 26.18 50.46 72.85 93.31 111.86 128.47 143.14 155.85
                166.60 175.38 }
              n.b element create e1 -xdata xVector -ydata yVector

       The advantage of using vectors is that when you modify one,  the  graph  is  automatically
       redrawn to reflect the new values.

              # Change the y coordinate of the first point.
              set yVector(0) 25.18

       An  element  named e1 is now created in .b.  It is automatically added to the display list
       of elements.  You can use this list to control in what order elements are  displayed.   To
       query or reset the element display list, you use the element's show operation.

              # Get the current display list
              set elemList [.b element show]
              # Remove the first element so it won't be displayed.
              .b element show [lrange $elemList 0 end]

       The element will be displayed by as many bars as there are data points (in this case there
       are ten).  The bars will be drawn centered at the x-coordinate of the data point.  All the
       bars  will  have  the same attributes (colors, stipple, etc).  The width of each bar is by
       default one unit.  You can change this with using the -barwidth option.

              # Change the scale of the x-coordinate data
              xVector set { 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 }
              # Make sure we change the bar width too.
              .b configure -barwidth 0.2

       The height of each bar is proportional to the ordinate (Y-coordinate) of the data point.

       If two or more  data  points  have  the  same  abscissa  (X-coordinate  value),  the  bars
       representing  those  data  points may be drawn in various ways.  The default is to overlay
       the bars, one on top of the other.  The ordering is determined from the of element display
       list.  If the stacked mode is selected (using the -barmode configuration option), the bars
       are stacked, each bar above the previous.

              # Display the elements as stacked.
              .b configure -barmode stacked

       If the aligned mode is selected, the bars having the same x-coordinates are displayed side
       by  side.   The width of each bar is a fraction of its normal width, based upon the number
       of bars with the same x-coordinate.

              # Display the elements side-by-side.
              .b configure -barmode aligned

       By default, the element's label in the legend will be also e1.  You can change the  label,
       or specify no legend entry, again using the element's configure operation.

              # Don't display "e1" in the legend.
              .b element configure e1 -label ""

       You can configure more than just the element's label.  An element has many attributes such
       as stipple, foreground and background colors, relief, etc.

              .b element configure e1 -fg red -bg pink \
                -stipple gray50

       Four coordinate axes are automatically created:  x,  x2,  y,  and  y2.   And  by  default,
       elements  are  mapped onto the axes x and y.  This can be changed with the -mapx and -mapy
       options.

              # Map "e1" on the alternate y axis "y2".
              .b element configure e1 -mapy y2

       Axes can be configured in many ways too.  For example, you change the scale of the  Y-axis
       from linear to log using the axis component.

              # Y-axis is log scale.
              .b axis configure y -logscale yes

       One  important  way  axes  are used is to zoom in on a particular data region.  Zooming is
       done by simply specifying new axis limits using the -min and -max configuration options.

              .b axis configure x -min 1.0 -max 1.5
              .b axis configure y -min 12.0 -max 55.15

       To zoom interactively, you link theaxis configure operations with  some  user  interaction
       (such  as  pressing  the mouse button), using the bind command.  To convert between screen
       and graph coordinates, use the invtransform operation.

              # Click the button to set a new minimum
              bind .b <ButtonPress-1> {
                  %W axis configure x -min [%W axis invtransform x %x]
                  %W axis configure x -min [%W axis invtransform x %y]
              }

       By default, the limits of the axis are determined from data values.  To reset back to  the
       default limits, set the -min and -max options to the empty value.

              # Reset the axes to autoscale again.
              .b axis configure x -min {} -max {}
              .b axis configure y -min {} -max {}

       By  default,  the  legend is drawn in the right margin.  You can change this or any legend
       configuration options using the legend component.

              # Configure the legend font, color, and relief
              .b legend configure -position left -relief raised \
                -font fixed -fg blue

       To prevent the legend from being displayed, turn on the -hide option.

              # Don't display the legend.
              .b legend configure -hide yes

       The barchart has simple drawing procedures called markers.  They can be used to  highlight
       or  annotate  data  in  the  graph.  The types of markers available are bitmaps, polygons,
       lines, or windows.  Markers can be used, for  example,  to  mark  or  brush  points.   For
       example  there  may  be  a  line marker which indicates some low-water value.  Markers are
       created using the marker operation.

              # Create a line represent the low water mark at 10.0
              .b marker create line -name "low_water" \
                -coords { -Inf 10.0 Inf 10.0 } \
                -dashes { 2 4 2 } -fg red -bg blue

       This creates a line marker named low_water.  It will display a horizontal line  stretching
       across  the  plotting  area  at  the  y-coordinate 10.0.  The coordinates "-Inf" and "Inf"
       indicate the relative minimum and maximum of the axis  (in  this  case  the  x-axis).   By
       default,  markers are drawn last, on top of the bars.  You can change this with the -under
       option.

              # Draw the marker before elements are drawn.
              .b marker configure low_water -under yes

       You can add cross hairs or grid lines using the crosshairs and grid components.

              # Display both cross hairs and grid lines.
              .b crosshairs configure -hide no -color red
              .b grid configure -hide no -dashes { 2 2 }

       Finally, to get hardcopy of the graph, use the postscript component.

              # Print the bar chart into file "file.ps"
              .b postscript output file.ps -maxpect yes -decorations no

       This generates a file file.ps containing the encapsulated PostScript of  the  graph.   The
       option  -maxpect  says  to  scale  the  plot  to  the  size  of the page.  Turning off the
       -decorations option denotes that no borders or color backgrounds should be drawn (i.e. the
       background of the margins, legend, and plotting area will be white).

SYNTAX

       barchart  pathName  ?option  value?...  The barchart command creates a new window pathName
       and makes it into a barchart widget.  At the time this command is invoked, there must  not
       exist  a  window named pathName, but pathName's parent must exist.  Additional options may
       may be specified on the command line or in the option database to configure aspects of the
       bar  chart  such  as its colors and font.  See the configure operation below for the exact
       details as to what option and value pairs are valid.

       If successful, barchart returns pathName. It also creates  a  new  Tcl  command  pathName.
       This  command  may  be used to invoke various operations to query or modify the bar chart.
       It has the general form: pathName operation ?arg?...  Both  operation  and  its  arguments
       determine  the  exact behavior of the command.  The operations available for the bar chart
       are described in the following section.

BARCHART OPERATIONS

       pathName bar elemName ?option value?...
              Creates a new barchart element elemName.  It's an  error  if  an  element  elemName
              already  exists.   See  the  manual  for barchart for details about what option and
              value pairs are valid.

       pathName cget option
              Returns the current value of the configuration option given by option.  Option  may
              be any option described below for the configure operation.

       pathName configure ?option value?...
              Queries  or  modifies  the  configuration  options  of  the graph.  If option isn't
              specified, a list describing the current options  for  pathName  is  returned.   If
              option  is specified, but not value, then a list describing option is returned.  If
              one or more option and value pairs are specified, then for each  pair,  the  option
              option is set to value.  The following options are valid.

              -background color
                     Sets the background color. This includes the margins and legend, but not the
                     plotting area.

              -barmode mode
                     Indicates how related bar elements will be  drawn.   Related  elements  have
                     data  points  with  the  same  abscissas (X-coordinates). Mode indicates how
                     those segments should be drawn. Mode can be infront,  aligned,  overlap,  or
                     stacked.  The default mode is infront.

                     infront   Each successive segment is drawn in front of the previous.

                     stacked   Each  successive  segment  is  stacked  vertically  on  top of the
                               previous.

                     aligned   Segments is displayed aligned from right-to-left.

                     overlap   Like aligned but segments slightly overlap each other.

              -barwidth value
                     Specifies the width of the  bars.   This  value  can  be  overrided  by  the
                     individual  elements  using  their -barwidth configuration option.  Value is
                     the width in terms of graph coordinates.  The default width is 1.0.

              -borderwidth pixels
                     Sets the width of the 3-D border around the outside edge of the widget.  The
                     -relief option determines if the border is to be drawn.  The default is 2.

              -bottommargin pixels
                     Specifies  the size of the margin below the X-coordinate axis.  If pixels is
                     0, the size of the margin is selected automatically.  The default is 0.

              -bufferelements boolean
                     Indicates whether an internal pixmap to buffer the display of data  elements
                     should  be used.  If boolean is true, data elements are drawn to an internal
                     pixmap.  This  option  is  especially  useful  when  the  graph  is  redrawn
                     frequently  while  the  remains data unchanged (for example, moving a marker
                     across the plot).  See the SPEED TIPS section.  The default is 1.

              -cursor cursor
                     Specifies the widget's cursor.  The default cursor is crosshair.

              -font fontName
                     Specifies the font of the graph title. The  default  is  *-Helvetica-Bold-R-
                     Normal-*-18-180-*.

              -halo pixels
                     Specifies a maximum distance to consider when searching for the closest data
                     point (see the element's closest operation below).  Data points further than
                     pixels away are ignored.  The default is 0.5i.

              -height pixels
                     Specifies the requested height of widget.  The default is 4i.

              -invertxy boolean
                     Indicates  whether  the  placement X-axis and Y-axis should be inverted.  If
                     boolean is true, the X and Y axes are swapped.  The default is 0.

              -justify justify
                     Specifies how the title should be justified.  This  matters  only  when  the
                     title  contains  more than one line of text. Justify must be left, right, or
                     center.  The default is center.

              -leftmargin pixels
                     Sets the size of the margin  from  the  left  edge  of  the  window  to  the
                     Y-coordinate  axis.   If  pixels is 0, the size is calculated automatically.
                     The default is 0.

              -plotbackground color
                     Specifies the background color of the plotting area.  The default is white.

              -plotborderwidth pixels
                     Sets the width of the 3-D border around the plotting area.  The  -plotrelief
                     option determines if a border is drawn.  The default is 2.

              -plotpadx pad
                     Sets  the  amount  of padding to be added to the left and right sides of the
                     plotting area.  Pad can be a list of one or two screen  distances.   If  pad
                     has  two elements, the left side of the plotting area entry is padded by the
                     first distance and the right side  by  the  second.   If  pad  is  just  one
                     distance,  both  the left and right sides are padded evenly.  The default is
                     8.

              -plotpady pad
                     Sets the amount of padding to be added to the top and bottom of the plotting
                     area.   Pad  can  be  a list of one or two screen distances.  If pad has two
                     elements, the top of the plotting area is padded by the first  distance  and
                     the  bottom  by  the  second.  If pad is just one distance, both the top and
                     bottom are padded evenly.  The default is 8.

              -plotrelief relief
                     Specifies the 3-D effect for the plotting area.  Relief  specifies  how  the
                     interior  of  the plotting area should appear relative to rest of the graph;
                     for example, raised means the plot should appear to protrude from the graph,
                     relative to the surface of the graph.  The default is sunken.

              -relief relief
                     Specifies  the 3-D effect for the barchart widget.  Relief specifies how the
                     graph should appear relative to widget  it  is  packed  into;  for  example,
                     raised means the graph should appear to protrude.  The default is flat.

              -rightmargin pixels
                     Sets  the  size  of  margin  from the plotting area to the right edge of the
                     window.  By default, the legend is drawn in this margin.  If pixels is  than
                     1, the margin size is selected automatically.

              -takefocus focus
                     Provides  information  used  when moving the focus from window to window via
                     keyboard traversal (e.g., Tab and Shift-Tab).  If focus  is  0,  this  means
                     that  this  window  should be skipped entirely during keyboard traversal.  1
                     means that the this window should always receive the input focus.  An  empty
                     value means that the traversal scripts make the decision whether to focus on
                     the window.  The default is "".

              -tile image
                     Specifies a tiled background  for  the  widget.   If  image  isn't  "",  the
                     background  is tiled using image.  Otherwise, the normal background color is
                     drawn (see the -background option).  Image must be an  image  created  using
                     the Tk image command.  The default is "".

              -title text
                     Sets the title to text. If text is "", no title will be displayed.

              -topmargin pixels
                     Specifies  the  size  of  the margin above the x2 axis.  If pixels is 0, the
                     margin size is calculated automatically.

              -width pixels
                     Specifies the requested width of the widget.  The default is 5i.

       pathName crosshairs operation ?arg?
              See the CROSSHAIRS COMPONENT section.

       pathName element operation ?arg?...
              See the ELEMENT COMPONENTS section.

       pathName extents item
              Returns the size  of  a  particular  item  in  the  graph.   Item  must  be  either
              leftmargin, rightmargin, topmargin, bottommargin, plotwidth, or plotheight.

       pathName grid operation ?arg?...
              See the GRID COMPONENT section.

       pathName invtransform winX winY
              Performs  an  inverse coordinate transformation, mapping window coordinates back to
              graph coordinates, using the  standard  X-axis  and  Y-axis.   Returns  a  list  of
              containing the X-Y graph coordinates.

       pathName inside x y
              Returns 1 is the designated screen coordinate (x and y) is inside the plotting area
              and 0 otherwise.

       pathName legend operation ?arg?...
              See the LEGEND COMPONENT section.

       pathName line operation arg...
              The operation is the same as element.

       pathName marker operation ?arg?...
              See the MARKER COMPONENTS section.

       pathName metafile ?fileName?
              This operation is for Window platforms only.  Creates a Windows  enhanced  metafile
              of  the  barchart.   If  present,  fileName  is  the file name of the new metafile.
              Otherwise, the metafile is automatically added to the clipboard.

       pathName postscript operation ?arg?...
              See the POSTSCRIPT COMPONENT section.

       pathName snap photoName
              Takes a snapshot of the graph and stores the contents in the photo image photoName.
              PhotoName is the name of a Tk photo image that must already exist.

       pathName transform x y
              Performs   a   coordinate  transformation,  mapping  graph  coordinates  to  window
              coordinates, using the standard X-axis and Y-axis.  Returns a list  containing  the
              X-Y screen coordinates.

       pathName xaxis operation ?arg?...

       pathName x2axis operation ?arg?...

       pathName yaxis operation ?arg?...

       pathName y2axis operation ?arg?...
              See the AXIS COMPONENTS section.

BARCHART COMPONENTS

       A  graph  is composed of several components: coordinate axes, data elements, legend, grid,
       cross hairs, postscript, and annotation markers. Instead of one big set  of  configuration
       options  and  operations,  the  graph  is  partitioned,  where  each component has its own
       configuration options and operations that specifically control that aspect or part of  the
       graph.

   AXIS COMPONENTS
       Four  coordinate  axes are automatically created: two X-coordinate axes (x and x2) and two
       Y-coordinate axes (y, and y2).  By default, the axis x is located in the bottom margin,  y
       in the left margin, x2 in the top margin, and y2 in the right margin.

       An  axis  consists of the axis line, title, major and minor ticks, and tick labels.  Major
       ticks are drawn at uniform intervals along the  axis.   Each  tick  is  labeled  with  its
       coordinate value.  Minor ticks are drawn at uniform intervals within major ticks.

       The  range  of  the axis controls what region of data is plotted.  Data points outside the
       minimum and maximum limits of the axis are not  plotted.   By  default,  the  minimum  and
       maximum limits are determined from the data, but you can reset either limit.

       You  can create and use several axes. To create an axis, invoke the axis component and its
       create operation.

              # Create a new axis called "temperature"
              .b axis create temperature

       You map data elements to an  axis  using  the  element's  -mapy  and  -mapx  configuration
       options. They specify the coordinate axes an element is mapped onto.

              # Now map the temperature data to this axis.
              .b element create "temp" -xdata $x -ydata $tempData \
                  -mapy temperature

       While  you  can  have many axes, only four axes can be displayed simultaneously.  They are
       drawn in each of the margins surrounding the plotting area.  The axes x and y are drawn in
       the  bottom and left margins. The axes x2 and y2 are drawn in top and right margins.  Only
       x and y are shown by default. Note that the axes can have different scales.

       To display a different axis, you invoke one of the  following  components:  xaxis,  yaxis,
       x2axis,  and  y2axis.   The  use  operation  designates  the  axis  to  be  drawn  in  the
       corresponding margin: xaxis in the bottom, yaxis in the  left,  x2axis  in  the  top,  and
       y2axis in the right.

              # Display the axis temperature in the left margin.
              .b yaxis use temperature

       You  can  configure  axes  in many ways. The axis scale can be linear or logarithmic.  The
       values along the axis can either monotonically increase or decrease.  If you  need  custom
       tick  labels,  you  can specify a Tcl procedure to format the label any way you wish.  You
       can control how ticks are drawn, by changing the major tick  interval  or  the  number  of
       minor ticks.  You can define non-uniform tick intervals, such as for time-series plots.

       pathName axis cget axisName option
              Returns  the  current value of the option given by option for axisName.  Option may
              be any option described below for the axis configure operation.

       pathName axis configure axisName ?axisName?... ?option value?...
              Queries or modifies the configuration options of axisName.   Several  axes  can  be
              changed.   If option isn't specified, a list describing all the current options for
              axisName is returned.   If  option  is  specified,  but  not  value,  then  a  list
              describing  option  is  returned.   If  one  or  more  option  and  value pairs are
              specified, then for each pair, the  axis  option  option  is  set  to  value.   The
              following options are valid for axes.

              -autorange range
                     Sets  the  range  of  values  for  the  axis  to range.  The axis limits are
                     automatically reset to display the most recent data points  in  this  range.
                     If  range  is  0.0, the range is determined from the limits of the data.  If
                     -min or -max are specified, they override this option.  The default is 0.0.

              -color color
                     Sets the color of the axis and tick labels.  The default is black.

              -command prefix
                     Specifies a Tcl command to be invoked when formatting the axis tick  labels.
                     Prefix is a string containing the name of a Tcl proc and any extra arguments
                     for the procedure.  This command is invoked for each major tick on the axis.
                     Two  additional  arguments  are passed to the procedure: the pathname of the
                     widget and the current the numeric value of the tick.  The procedure returns
                     the  formatted  tick label.  If "" is returned, no label will appear next to
                     the tick.  You can get the standard tick labels again by setting  prefix  to
                     "".  The default is "".

                     Please  note  that this procedure is invoked while the bar chart is redrawn.
                     You may query the widget's configuration options.  But do not reset options,
                     because this can have unexpected results.

              -descending boolean
                     Indicates  whether the values along the axis are monotonically increasing or
                     decreasing.  If boolean is true, the axis values will  be  decreasing.   The
                     default is 0.

              -hide boolean
                     Indicates whether the axis is displayed.

              -justify justify
                     Specifies  how  the  axis title should be justified.  This matters only when
                     the axis title contains more than one line of text. Justify  must  be  left,
                     right, or center.  The default is center.

              -limits formatStr
                     Specifies a printf-like description to format the minimum and maximum limits
                     of the axis.  The limits are displayed at the top/bottom or left/right sides
                     of   the  plotting  area.   FormatStr  is  a  list  of  one  or  two  format
                     descriptions.  If one description is supplied, both the minimum and  maximum
                     limits  are  formatted  in  the  same way.  If two, the first designates the
                     format for the minimum limit, the second for the maximum.  If "" is given as
                     either  description, then the that limit will not be displayed.  The default
                     is "".

              -linewidth pixels
                     Sets the width of the axis and tick lines.  The default is 1 pixel.

              -logscale boolean
                     Indicates whether the scale of  the  axis  is  logarithmic  or  linear.   If
                     boolean is true, the axis is logarithmic.  The default scale is linear.

              -loose boolean
                     Indicates whether the limits of the axis should fit the data points tightly,
                     at the outermost data points, or loosely, at the outer tick intervals.  This
                     is  relevant  only  when  the  axis  limit  is automatically calculated.  If
                     boolean is true, the axis range is "loose".  The default is 0.

              -majorticks majorList
                     Specifies where to display major axis ticks.  You can  use  this  option  to
                     display  ticks  at  non-uniform  intervals.   MajorList  is  a  list of axis
                     coordinates designating the location of major ticks.   No  minor  ticks  are
                     drawn.   If majorList is "", major ticks will be automatically computed. The
                     default is "".

              -max value
                     Sets the maximum limit of axisName.  Any data point greater  than  value  is
                     not  displayed.   If  value is "", the maximum limit is calculated using the
                     largest data value.  The default is "".

              -min value
                     Sets the minimum limit of axisName. Any data point less than  value  is  not
                     displayed.   If  value  is  "",  the  minimum  limit is calculated using the
                     smallest data value.  The default is "".

              -minorticks minorList
                     Specifies where to display minor axis ticks.  You can  use  this  option  to
                     display  minor  ticks  at non-uniform intervals. MinorList is a list of real
                     values, ranging from 0.0 to 1.0, designating the placement of a minor  tick.
                     No minor ticks are drawn if the -majortick option is also set.  If minorList
                     is "", minor ticks will be automatically computed. The default is "".

              -rotate theta
                     Specifies the how many degrees to rotate the axis tick labels.  Theta  is  a
                     real  value  representing  the  number of degrees to rotate the tick labels.
                     The default is 0.0 degrees.

              -shiftby value
                     Specifies how much to automatically shift the range of the axis.   When  the
                     new  data  exceeds  the  current  axis  maximum, the maximum is increased in
                     increments of value.  You can use this option to  prevent  the  axis  limits
                     from  being  recomputed  at  each  new  time point. If value is 0.0, then no
                     automatic shifting is down. The default is 0.0.

              -showticks boolean
                     Indicates whether axis ticks should be drawn. If boolean is true, ticks  are
                     drawn.  If false, only the axis line is drawn. The default is 1.

              -stepsize value
                     Specifies  the  interval  between  major axis ticks.  If value isn't a valid
                     interval (must be less than the axis range), the request is ignored and  the
                     step size is automatically calculated.

              -subdivisions number
                     Indicates how many minor axis ticks are to be drawn.  For example, if number
                     is two, only one minor tick is drawn.  If number is one, no minor ticks  are
                     displayed.  The default is 2.

              -tickfont fontName
                     Specifies  the  font  for axis tick labels. The default is *-Courier-Bold-R-
                     Normal-*-100-*.

              -ticklength pixels
                     Sets the length of major and minor ticks (minor ticks are half the length of
                     major  ticks).  If  pixels is less than zero, the axis will be inverted with
                     ticks drawn pointing towards the plot.  The default is 0.1i.

              -title text
                     Sets the title of the axis. If text is "", no axis title will be displayed.

              -titlecolor color
                     Sets the color of the axis title. The default is black.

              -titlefont fontName
                     Specifies the font  for  axis  title.  The  default  is  *-Helvetica-Bold-R-
                     Normal-*-14-140-*.

              Axis  configuration options may be also be set by the option command.  The resource
              class is Axis.  The resource names are the names of the axes (such as x or x2).

                     option add *Barchart.Axis.Color  blue
                     option add *Barchart.x.LogScale  true
                     option add *Barchart.x2.LogScale false

       pathName axis create axisName ?option value?...
              Creates a new axis by the name axisName.  No axis by  the  same  name  can  already
              exist. Option and value are described in above in the axis configure operation.

       pathName axis delete ?axisName?...
              Deletes  the  named  axes.  An axis is not really deleted until it is not longer in
              use, so it's safe to delete axes mapped to elements.

       pathName axis invtransform axisName value
              Performs the inverse transformation, changing the  screen  coordinate  value  to  a
              graph  coordinate,  mapping  the  value  mapped  to  axisName.   Returns  the graph
              coordinate.

       pathName axis limits axisName
              Returns a list of the minimum and maximum limits for axisName.  The  order  of  the
              list is min max.

       pathName axis names ?pattern?...
              Returns  a  list of axes matching zero or more patterns.  If no pattern argument is
              give, the names of all axes are returned.

       pathName axis transform axisName value
              Transforms the coordinate value to  a  screen  coordinate  by  mapping  the  it  to
              axisName.  Returns the transformed screen coordinate.

       Only  four  axes  can be displayed simultaneously.  By default, they are x, y, x2, and y2.
       You can swap in a different axis with use operation of the special axis components: xaxis,
       x2axis, yaxis, and y2axis.

              .g create axis temp
              .g create axis time
              ...
              .g xaxis use temp
              .g yaxis use time

       Only the axes specified for use are displayed on the screen.

       The  xaxis, x2axis, yaxis, and y2axis components operate on an axis location rather than a
       specific axis like the more general axis component does.  The xaxis component manages  the
       X-axis  located  in the bottom margin (whatever axis that happens to be).  Likewise, yaxis
       uses the Y-axis in the left margin, x2axis the top X-axis, and y2axis the right Y-axis.

       They implicitly control the axis that is currently using to that  location.   By  default,
       xaxis uses the x axis, yaxis uses y, x2axis uses x2, and y2axis uses y2.  These components
       can be more convenient to  use  than  always  determining  what  axes  are  current  being
       displayed by the graph.

       The following operations are available for axes. They mirror exactly the operations of the
       axis component.  The axis argument must be xaxis, x2axis, yaxis, or y2axis.

       pathName axis cget option

       pathName axis configure ?option value?...

       pathName axis invtransform value

       pathName axis limits

       pathName axis transform value

       pathName axis use ?axisName?
              Designates the axis axisName is to be displayed at this location.  AxisName can not
              be  already  in use at another location.  This command returns the name of the axis
              currently using this location.

   CROSSHAIRS COMPONENT
       Cross hairs consist of two intersecting lines (one  vertical  and  one  horizontal)  drawn
       completely  across  the plotting area.  They are used to position the mouse in relation to
       the coordinate axes.  Cross hairs differ from line markers in that  they  are  implemented
       using  XOR  drawing  primitives.   This  means  that  they can be quickly drawn and erased
       without redrawing the entire widget.

       The following operations are available for cross hairs:

       pathName crosshairs cget option
              Returns the current value of the cross hairs configuration option given by  option.
              Option may be any option described below for the cross hairs configure operation.

       pathName crosshairs configure ?option value?...
              Queries  or modifies the configuration options of the cross hairs.  If option isn't
              specified, a list describing all  the  current  options  for  the  cross  hairs  is
              returned.   If option is specified, but not value, then a list describing option is
              returned.  If one or more option and value pairs are specified, then for each pair,
              the cross hairs option option is set to value.  The following options are available
              for cross hairs.

              -color color
                     Sets the color of the cross hairs.  The default is black.

              -dashes dashList
                     Sets the dash style of the cross hairs. DashList is  a  list  of  up  to  11
                     numbers that alternately represent the lengths of the dashes and gaps on the
                     cross hair lines.  Each number must be between 1 and 255.   If  dashList  is
                     "", the cross hairs will be solid lines.

              -hide boolean
                     Indicates whether cross hairs are drawn. If boolean is true, cross hairs are
                     not drawn.  The default is yes.

              -linewidth pixels
                     Set the width of the cross hair lines.  The default is 1.

              -position pos
                     Specifies the screen position where the cross hairs intersect.  Pos must  be
                     in  the  form  "@x,y",  where  x  and  y  are  the window coordinates of the
                     intersection.

              Cross hairs configuration options may be also be set by the  option  command.   The
              resource name and class are crosshairs and Crosshairs respectively.

                     option add *Barchart.Crosshairs.LineWidth 2
                     option add *Barchart.Crosshairs.Color     red

       pathName crosshairs off
              Turns off the cross hairs.

       pathName crosshairs on
              Turns on the display of the cross hairs.

       pathName crosshairs toggle
              Toggles the current state of the cross hairs, alternately mapping and unmapping the
              cross hairs.

ELEMENTS

       A data element represents a set of data.  It contains  x  and  y  vectors  which  are  the
       coordinates  of  the  data points.  Elements are displayed as bars where the length of the
       bar is proportional to the  ordinate  of  the  data  point.   Elements  also  control  the
       appearance of the data, such as the color, stipple, relief, etc.

       When  new  data  elements are created, they are automatically added to a list of displayed
       elements.   The display list controls what elements are drawn and in what order.

       The following operations are available for elements.

       pathName element activate elemName ?index?...
              Specifies the data points of element elemName to be drawn using  active  foreground
              and  background  colors.  ElemName is the name of the element and index is a number
              representing the index of the data point. If no indices are present then  all  data
              points become active.

       pathName element bind tagName ?sequence?  ?command?
              Associates  command  with  tagName  such  that whenever the event sequence given by
              sequence occurs for an element with this tag, command will be invoked.  The  syntax
              is  similar  to  the bind command except that it operates on graph elements, rather
              than widgets. See the bind manual entry for complete details on  sequence  and  the
              substitutions performed on command before invoking it.

              If  all  arguments  are  specified  then  a  new  binding is created, replacing any
              existing binding for the same sequence and tagName.   If  the  first  character  of
              command  is  +  then command augments an existing binding rather than replacing it.
              If no command argument is provided  then  the  command  currently  associated  with
              tagName and sequence (it's an error occurs if there's no such binding) is returned.
              If both command and sequence are missing then a list of all the event sequences for
              which bindings have been defined for tagName.

       pathName element cget elemName option
              Returns  the  current  value  of  the element configuration option given by option.
              Option may be any  of  the  options  described  below  for  the  element  configure
              operation.

       pathName element closest x y ?option value?... ?elemName?...
              Finds the data point representing the bar closest to the window coordinates x and y
              in the element elemName.  ElemName is  the  name  of  an  element,  which  must  be
              displayed.  If no elements are specified, then all displayed elements are searched.
              It returns a list containing the name of the closest  element,  the  index  of  its
              closest  point, and the graph coordinates of the point. If no data point within the
              threshold distance can be found, "" is returned.  The following option-value  pairs
              are available.

              -halo pixels
                     Specifies  a  threshold  distance  where  selected  data points are ignored.
                     Pixels is a valid screen distance, such as 2 or 1.2i.  If this option  isn't
                     specified, then it defaults to the value of the barchart's -halo option.

       pathName element configure elemName ?elemName... ?option value?...
              Queries  or  modifies the configuration options for elements.  Several elements can
              be modified at the same time. If option isn't specified, a list describing all  the
              current  options  for elemName is returned.  If option is specified, but not value,
              then a list describing the option option is returned.  If one or  more  option  and
              value  pairs are specified, then for each pair, the element option option is set to
              value.  The following options are valid for elements.

              -activepen penName
                     Specifies pen to use to draw active element.  If penName is  "",  no  active
                     elements will be drawn.  The default is activeLine.

              -bindtags tagList
                     Specifies  the  binding  tags for the element.  TagList is a list of binding
                     tag names.  The tags and their order will determine how events for elements.
                     Each  tag  in the list matching the current event sequence will have its Tcl
                     command executed.  Implicitly the name of the element is  always  the  first
                     tag in the list.  The default value is all.

              -background color
                     Sets the the color of the border around each bar.  The default is white.

              -barwidth value
                     Specifies  the  width the bars drawn for the element.  Value is the width in
                     X-coordinates.  If this option isn't specified, the width of each bar is the
                     value of the widget's -barwidth option.

              -baseline value
                     Specifies the baseline of the bar segments.  This affects how bars are drawn
                     since bars are drawn from their respective  y-coordinate  the  baseline.  By
                     default the baseline is 0.0.

              -borderwidth pixels
                     Sets  the  border  width  of the 3-D border drawn around the outside of each
                     bar.  The -relief option determines if such a border is drawn.  Pixels  must
                     be a valid screen distance like 2 or 0.25i. The default is 2.

              -data coordList
                     Specifies  the  X-Y coordinates of the data.  CoordList is a list of numeric
                     expressions representing the X-Y coordinate pairs of each data point.

              -foreground color
                     Sets the color of the interior of the bars.

              -hide boolean
                     Indicates whether the element is displayed.  The default is no.

              -label text
                     Sets the element's label in the legend.  If text is  "",  the  element  will
                     have no entry in the legend.  The default label is the element's name.

              -mapx xAxis
                     Selects  the  X-axis to map the element's X-coordinates onto.  XAxis must be
                     the name of an axis.  The default is x.

              -mapy yAxis
                     Selects the Y-axis to map the element's Y-coordinates onto.  YAxis  must  be
                     the name of an axis. The default is y.

              -relief string
                     Specifies  the  3-D  effect  desired  for  bars.   Relief  indicates how the
                     interior of the bar should appear relative to the surface of the chart;  for
                     example,  raised means the bar should appear to protrude from the surface of
                     the plotting area.  The default is raised.

              -stipple bitmap
                     Specifies a stipple pattern with which to draw the bars.  If bitmap  is  "",
                     then the bar is drawn in a solid fashion.

              -xdata xVector
                     Specifies the x-coordinate vector of the data.  XVector is the name of a BLT
                     vector or a list of numeric expressions.

              -ydata yVector
                     Specifies the y-coordinate vector of the data.  YVector is the name of a BLT
                     vector or a list of numeric expressions.

              Element  configuration options may also be set by the option command.  The resource
              names  in the option database are prefixed by elem.

                     option add *Barchart.Element.background blue

       pathName element create elemName ?option value?...
              Creates a new element elemName.  Element  names  must  be  unique,  so  an  element
              elemName  may not already exist.  If additional arguments are present, they specify
              any of the element options valid for element configure operation.

       pathName element deactivate pattern...
              Deactivates all the elements matching pattern for the graph.  Elements whose  names
              match any of the patterns given are redrawn using their normal colors.

       pathName element delete ?pattern?...
              Deletes  all  the  elements  matching  pattern for the graph.  Elements whose names
              match any of the patterns given are deleted.  The graph will be redrawn without the
              deleted elements.

       pathName element exists elemName
              Returns 1 if an element elemName currently exists and 0 otherwise.

       pathName element names ?pattern?...
              Returns  the  elements  matching  one or more pattern.  If no pattern is given, the
              names of all elements is returned.

       pathName element show ?nameList?
              Queries or modifies the element display list.  The element display list  designates
              the  elements  drawn  and  in  what  order.  NameList  is  a list of elements to be
              displayed in the order they are named.  If  there  is  no  nameList  argument,  the
              current display list is returned.

       pathName element type elemName
              Returns  the  type  of  elemName.   If  the  element is a bar element, the commands
              returns the string "bar", otherwise it returns "line".

   GRID COMPONENT
       Grid lines extend from the major and minor ticks of each axis horizontally  or  vertically
       across the plotting area.  The following operations are available for grid lines.

       pathName grid cget option
              Returns  the  current  value of the grid line configuration option given by option.
              Option may be any option described below for the grid configure operation.

       pathName grid configure ?option value?...
              Queries or modifies the configuration options for  grid  lines.   If  option  isn't
              specified, a list describing all the current grid options for pathName is returned.
              If option is specified, but not value, then a list describing option  is  returned.
              If  one  or more option and value pairs are specified, then for each pair, the grid
              line option option is set to value.  The  following  options  are  valid  for  grid
              lines.

              -color color
                     Sets the color of the grid lines.  The default is black.

              -dashes dashList
                     Sets  the  dash  style  of  the  grid  lines. DashList is a list of up to 11
                     numbers that alternately represent the lengths of the dashes and gaps on the
                     grid  lines.  Each number must be between 1 and 255.  If dashList is "", the
                     grid will be solid lines.

              -hide boolean
                     Indicates whether the grid should be drawn. If boolean is true,  grid  lines
                     are not shown. The default is yes.

              -linewidth pixels
                     Sets the width of grid lines.  The default width is 1.

              -mapx xAxis
                     Specifies  the  X-axis  to display grid lines.  XAxis must be the name of an
                     axis or "" for no grid lines.  The default is "".

              -mapy yAxis
                     Specifies the Y-axis to display grid lines.  YAxis must be the  name  of  an
                     axis or "" for no grid lines.  The default is y.

              -minor boolean
                     Indicates  whether  the  grid  lines  should  be  drawn for minor ticks.  If
                     boolean is true, the lines will appear at minor tick intervals.  The default
                     is 1.

              Grid  configuration  options  may  also be set by the option command.  The resource
              name and class are grid and Grid respectively.

                     option add *Barchart.grid.LineWidth 2
                     option add *Barchart.Grid.Color     black

       pathName grid off
              Turns off the display the grid lines.

       pathName grid on
              Turns on the display the grid lines.

       pathName grid toggle
              Toggles the display of the grid.

   LEGEND COMPONENT
       The legend displays a list of the data elements.  Each entry  consists  of  the  element's
       symbol  and  label.   The  legend can appear in any margin (the default location is in the
       right margin).  It can also be positioned anywhere within the plotting area.

       The following operations are valid for the legend.

       pathName legend activate pattern...
              Selects legend entries to be drawn using the active legend colors and relief.   All
              entries  whose  element  names  match  pattern   are selected.  To be selected, the
              element name must match only one pattern.

       pathName legend bind tagName ?sequence?  ?command?
              Associates command with tagName such that whenever  the  event  sequence  given  by
              sequence  occurs  for  a  legend  entry  with  this  tag,  command will be invoked.
              Implicitly the element names in the entry are tags.  The syntax is similar  to  the
              bind  command  except  that it operates on legend entries, rather than widgets. See
              the bind manual entry for  complete  details  on  sequence  and  the  substitutions
              performed on command before invoking it.

              If  all  arguments  are  specified  then  a  new  binding is created, replacing any
              existing binding for the same sequence and tagName.   If  the  first  character  of
              command  is  +  then command augments an existing binding rather than replacing it.
              If no command argument is provided  then  the  command  currently  associated  with
              tagName and sequence (it's an error occurs if there's no such binding) is returned.
              If both command and sequence are missing then a list of all the event sequences for
              which bindings have been defined for tagName.

       pathName legend cget option
              Returns  the  current  value  of  a legend configuration option.  Option may be any
              option described below in the legend configure operation.

       pathName legend configure ?option value?...
              Queries or modifies the configuration options for  the  legend.   If  option  isn't
              specified,  a  list describing the current legend options for pathName is returned.
              If option is specified, but not value, then a list describing option  is  returned.
              If one or more option and value pairs are specified, then for each pair, the legend
              option option is set to value.  The following options are valid for the legend.

              -activebackground color
                     Sets the background color for active legend  entries.   All  legend  entries
                     marked  active  (see  the  legend  activate  operation) are drawn using this
                     background color.

              -activeborderwidth pixels
                     Sets the width of the 3-D border around  the  outside  edge  of  the  active
                     legend entries.  The default is 2.

              -activeforeground color
                     Sets  the  foreground  color  for active legend entries.  All legend entries
                     marked as active (see the legend activate operation) are  drawn  using  this
                     foreground color.

              -activerelief relief
                     Specifies  the 3-D effect desired for active legend entries.  Relief denotes
                     how the interior of the entry should appear  relative  to  the  legend;  for
                     example,  raised  means the entry should appear to protrude from the legend,
                     relative to the surface of the legend.  The default is flat.

              -anchor anchor
                     Tells how to position the legend relative to the positioning point  for  the
                     legend.   This  is  dependent  on  the  value  of the -position option.  The
                     default is center.

                     left or right
                                 The anchor describes how to position the legend vertically.

                     top or bottom
                                 The anchor describes how to position the legend horizontally.

                     @x,y        The anchor specifies how to position the legend relative to  the
                                 positioning  point.  For  example,  if anchor is center then the
                                 legend is centered on the point; if anchor is n then the  legend
                                 will  be drawn such that the top center point of the rectangular
                                 region occupied by the legend will be at the positioning point.

                     plotarea    The anchor specifies how to position the legend relative to  the
                                 plotting  area. For example, if anchor is center then the legend
                                 is centered in the plotting area;  if  anchor  is  ne  then  the
                                 legend  will  be drawn such that occupies the upper right corner
                                 of the plotting area.

              -background color
                     Sets the background color  of  the  legend.  If  color  is  "",  the  legend
                     background with be transparent.

              -bindtags tagList
                     Specifies the binding tags for legend entries.  TagList is a list of binding
                     tag names.  The tags and their order will determine how  events  for  legend
                     entries.  Each tag in the list matching the current event sequence will have
                     its Tcl command executed. The default value is all.

              -borderwidth pixels
                     Sets the width of the 3-D border around the outside edge of the  legend  (if
                     such border is being drawn; the relief option determines this).  The default
                     is 2 pixels.

              -font fontName
                     FontName specifies a font to use when drawing the  labels  of  each  element
                     into the legend.  The default is *-Helvetica-Bold-R-Normal-*-12-120-*.

              -foreground color
                     Sets  the  foreground  color of the text drawn for the element's label.  The
                     default is black.

              -hide boolean
                     Indicates whether the legend should be displayed. If boolean  is  true,  the
                     legend will not be draw.  The default is no.

              -ipadx pad
                     Sets  the amount of internal padding to be added to the width of each legend
                     entry.  Pad can be a list of one or two screen distances.  If  pad  has  two
                     elements,  the left side of the legend entry is padded by the first distance
                     and the right side by the second.  If pad is just  one  distance,  both  the
                     left and right sides are padded evenly.  The default is 2.

              -ipady pad
                     Sets  an amount of internal padding to be added to the height of each legend
                     entry.  Pad can be a list of one or two screen distances.  If  pad  has  two
                     elements,  the  top  of  the  entry  is padded by the first distance and the
                     bottom by the second.  If pad is just one distance, both the top and  bottom
                     of the entry are padded evenly.  The default is 2.

              -padx pad
                     Sets  the padding to the left and right exteriors of the legend.  Pad can be
                     a list of one or two screen distances.  If pad has two  elements,  the  left
                     side of the legend is padded by the first distance and the right side by the
                     second.  If pad has just one distance, both the left  and  right  sides  are
                     padded evenly.  The default is 4.

              -pady pad
                     Sets  the  padding  above and below the legend.  Pad can be a list of one or
                     two screen distances.  If pad has two elements, the area above the legend is
                     padded  by  the  first distance and the area below by the second.  If pad is
                     just one distance, both the top and bottom areas  are  padded  evenly.   The
                     default is 0.

              -position pos
                     Specifies  where  the legend is drawn. The -anchor option also affects where
                     the legend is positioned.  If pos is left, left, top, or bottom, the  legend
                     is  drawn  in  the specified margin.  If pos is plotarea, then the legend is
                     drawn inside the plotting area at a particular anchor.  If  pos  is  in  the
                     form  "@x,y",  where x and y are the window coordinates, the legend is drawn
                     in the plotting area at the specified coordinates.  The default is right.

              -raised boolean
                     Indicates whether the legend is above or  below  the  data  elements.   This
                     matters only if the legend is in the plotting area.  If boolean is true, the
                     legend will be drawn on top of any elements that may overlap it. The default
                     is no.

              -relief relief
                     Specifies the 3-D effect for the border around the legend.  Relief specifies
                     how the interior of the legend should appear relative to the bar chart;  for
                     example,  raised  means  the  legend  should appear to protrude from the bar
                     chart, relative to the surface of the bar chart.  The default is sunken.

              Legend configuration options may also be set by the option command.   The  resource
              name and class are legend and Legend respectively.

                     option add *Barchart.legend.Foreground blue
                     option add *Barchart.Legend.Relief     raised

       pathName legend deactivate pattern...
              Selects  legend entries to be drawn using the normal legend colors and relief.  All
              entries whose element names match  pattern  are  selected.   To  be  selected,  the
              element name must match only one pattern.

       pathName legend get pos
              Returns  the  name  of the element whose entry is at the screen position pos in the
              legend.  Pos must be in the form "@x,y", where x and y are window coordinates.   If
              the given coordinates do not lie over a legend entry, "" is returned.

   PEN COMPONENTS
       Pens  define  attributes  for  elements.   Pens  mirror  the configuration options of data
       elements that pertain to how symbols and lines are  drawn.   Data  elements  use  pens  to
       determine how they are drawn.  A data element may use several pens at once.  In this case,
       the pen used for a particular data point is determined from each element's  weight  vector
       (see the element's -weight and -style options).

       One  pen, called activeBar, is automatically created.  It's used as the default active pen
       for elements. So you  can  change  the  active  attributes  for  all  elements  by  simply
       reconfiguring this pen.

              .g pen configure "activeBar" -fg green -bg green4

       You  can  create  and  use several pens. To create a pen, invoke the pen component and its
       create operation.

              .g pen create myPen

       You map pens to a data element using either the element's -pen or -activepen options.

              .g element create "e1" -xdata $x -ydata $tempData \
                  -pen myPen

       An element can use several pens at once. This is done by specifying the name of the pen in
       the element's style list (see the -styles option).

              .g element configure "e1" -styles { myPen 2.0 3.0 }

       This  says  that any data point with a weight between 2.0 and 3.0 is to be drawn using the
       pen myPen.  All other points are drawn with the element's default attributes.

       The following operations are available for pen components.

       pathName pen cget penName option
              Returns the current value of the option given by option for penName.  Option may be
              any option described below for the pen configure operation.

       pathName pen configure penName ?penName... ?option value?...
              Queries  or  modifies  the  configuration  options  of penName. Several pens can be
              modified at once.  If option isn't specified, a list describing the current options
              for  penName  is  returned.   If  option  is  specified, but not value, then a list
              describing option is  returned.   If  one  or  more  option  and  value  pairs  are
              specified,  then  for  each  pair,  the  pen  option  option  is set to value.  The
              following options are valid for pens.

              -background color
                     Sets the the color of the border around each bar.  The default is white.

              -borderwidth pixels
                     Sets the border width of the 3-D border drawn around  the  outside  of  each
                     bar.   The -relief option determines if such a border is drawn.  Pixels must
                     be a valid screen distance like 2 or 0.25i. The default is 2.

              -foreground color
                     Sets the color of the interior of the bars.

              -relief string
                     Specifies the 3-D  effect  desired  for  bars.   Relief  indicates  how  the
                     interior  of the bar should appear relative to the surface of the chart; for
                     example, raised means the bar should appear to protrude from the bar  chart,
                     relative to the surface of the plotting area.  The default is raised.

              -stipple bitmap
                     Specifies  a  stipple pattern with which to draw the bars.  If bitmap is "",
                     then the bar is drawn in a solid fashion.

              -type elemType
                     Specifies the type of element the pen is  to  be  used  with.   This  option
                     should  only be employed when creating the pen.  This is for those that wish
                     to mix different types of elements (bars and lines) on the same graph.   The
                     default type is "bar".

              Pen  configuration  options may be also be set by the option command.  The resource
              class is Pen.  The resource names are the names of the pens.

                     option add *Barchart.Pen.Foreground   blue
                     option add *Barchart.activeBar.foreground  green

       pathName pen create penName ?option value?...
              Creates a new pen by the name penName.  No pen by the same name can already  exist.
              Option and value are described in above in the pen configure operation.

       pathName pen delete ?penName?...
              Deletes  the named pens. A pen is not really deleted until it is not longer in use,
              so it's safe to delete pens mapped to elements.

       pathName pen names ?pattern?...
              Returns a list of pens matching zero or more patterns.  If no pattern  argument  is
              give, the names of all pens are returned.

   POSTSCRIPT COMPONENT
       The barchart can generate encapsulated PostScript output.  There are several configuration
       options you can specify to control how the plot will be generated.   You  can  change  the
       page  dimensions  and  borders.   The  plot  itself can be scaled, centered, or rotated to
       landscape.  The PostScript output can be written directly to a file  or  returned  through
       the interpreter.

       The following postscript operations are available.

       pathName postscript cget option
              Returns  the current value of the postscript option given by option.  Option may be
              any option described below for the postscript configure operation.

       pathName postscript configure ?option value?...
              Queries or modifies the configuration options for PostScript generation.  If option
              isn't  specified,  a list describing the current postscript options for pathName is
              returned.  If option is specified, but not value, then a list describing option  is
              returned.  If one or more option and value pairs are specified, then for each pair,
              the postscript option option is set to value.  The following postscript options are
              available.

              -center boolean
                     Indicates  whether  the  plot should be centered on the PostScript page.  If
                     boolean is false, the plot will be placed in the upper left  corner  of  the
                     page.  The default is 1.

              -colormap varName
                     VarName  must  be the name of a global array variable that specifies a color
                     mapping from the X color name to PostScript.  Each element of  varName  must
                     consist  of  PostScript code to set a particular color value (e.g. ``1.0 1.0
                     0.0 setrgbcolor'').  When generating color information  in  PostScript,  the
                     array  variable  varName  is  checked if an element of the name as the color
                     exists. If so, it uses its value as the PostScript command to set the color.
                     If  this option hasn't been specified, or if there isn't an entry in varName
                     for a given color, then it uses the red, green, and  blue  intensities  from
                     the X color.

              -colormode mode
                     Specifies  how  to output color information.  Mode must be either color (for
                     full  color  output),  gray  (convert  all  colors   to   their   gray-scale
                     equivalents)  or  mono  (convert  foreground  colors to black and background
                     colors to white).  The default mode is color.

              -fontmap varName
                     VarName must be the name of a global array variable that  specifies  a  font
                     mapping  from  the  X font name to PostScript.  Each element of varName must
                     consist of a Tcl list with one or two elements; the name and point size of a
                     PostScript font.  When outputting PostScript commands for a particular font,
                     the array variable varName is checked to see if an element by the  specified
                     font  exists.   If  there  is  such  an  element,  then the font information
                     contained in that element is used in the PostScript output.  (If  the  point
                     size  is  omitted  from  the  list,  the  point size of the X font is used).
                     Otherwise the X font is examined in an attempt to guess what PostScript font
                     to  use.  This works only for fonts whose foundry property is Adobe (such as
                     Times, Helvetica, Courier, etc.).  If  all  of  this  fails  then  the  font
                     defaults to Helvetica-Bold.

              -decorations boolean
                     Indicates  whether PostScript commands to generate color backgrounds and 3-D
                     borders will be output.  If boolean is false, the graph will background will
                     be white and no 3-D borders will be generated. The default is 1.

              -height pixels
                     Sets  the  height  of  the  plot.   This lets you print the bar chart with a
                     height different from the one drawn on the screen.   If  pixels  is  0,  the
                     height is the same as the widget's height.  The default is 0.

              -landscape boolean
                     If  boolean  is  true,  this  specifies the printed area is to be rotated 90
                     degrees.  In non-rotated output the X-axis of the printed  area  runs  along
                     the  short  dimension  of  the  page  (``portrait'' orientation); in rotated
                     output the X-axis runs along the long dimension of the  page  (``landscape''
                     orientation).  Defaults to 0.

              -maxpect boolean
                     Indicates  to  scale  the  plot  so  that it fills the PostScript page.  The
                     aspect ratio of the barchart is still retained.  The default is 0.

              -padx pad
                     Sets the horizontal padding for  the  left  and  right  page  borders.   The
                     borders  are  exterior  to the plot.  Pad can be a list of one or two screen
                     distances.  If pad has two elements, the left border is padded by the  first
                     distance  and the right border by the second.  If pad has just one distance,
                     both the left and right borders are padded evenly.  The default is 1i.

              -pady pad
                     Sets the vertical padding for the top and bottom page borders.  The  borders
                     are exterior to the plot.  Pad can be a list of one or two screen distances.
                     If pad has two elements, the top border is padded by the first distance  and
                     the bottom border by the second.  If pad has just one distance, both the top
                     and bottom borders are padded evenly.  The default is 1i.

              -paperheight pixels
                     Sets the height of the postscript page.  This can be used to select  between
                     different page sizes (letter, A4, etc).  The default height is 11.0i.

              -paperwidth pixels
                     Sets  the  width of the postscript page.  This can be used to select between
                     different page sizes (letter, A4, etc).  The default width is 8.5i.

              -width pixels
                     Sets the width of the plot.  This lets  you  generate  a  plot  of  a  width
                     different from that of the widget.  If pixels is 0, the width is the same as
                     the widget's width.  The default is 0.

              Postscript configuration options may be also be set by  the  option  command.   The
              resource name and class are postscript and Postscript respectively.

                     option add *Barchart.postscript.Decorations false
                     option add *Barchart.Postscript.Landscape   true

       pathName postscript output ?fileName? ?option value?...
              Outputs  a  file of encapsulated PostScript.  If a fileName argument isn't present,
              the command returns the PostScript. If any option-value pairs are present, they set
              configuration  options  controlling  how  the  PostScript is generated.  Option and
              value can be anything accepted by the postscript configure operation above.

   MARKER COMPONENTS
       Markers are simple drawing procedures used to annotate or highlight areas  of  the  graph.
       Markers  have  various  types: text strings, bitmaps, images, connected lines, windows, or
       polygons.  They can be associated with a particular element, so that when the  element  is
       hidden  or  un-hidden, so is the marker.  By default, markers are the last items drawn, so
       that data elements will appear in behind them.  You can change  this  by  configuring  the
       -under option.

       Markers,  in  contrast to elements, don't affect the scaling of the coordinate axes.  They
       can also have elastic coordinates (specified by -Inf and Inf respectively) that  translate
       into  the minimum or maximum limit of the axis.  For example, you can place a marker so it
       always remains in the lower left corner of the plotting area,  by  using  the  coordinates
       -Inf,-Inf.

       The following operations are available for markers.

       pathName marker after markerId ?afterId?
              Changes the order of the markers, drawing the first marker after the second.  If no
              second afterId argument is specified, the marker  is  placed  at  the  end  of  the
              display  list.  This command can be used to control how markers are displayed since
              markers are drawn in the order of this display list.

       pathName marker before markerId ?beforeId?
              Changes the order of the markers, drawing the first marker before the  second.   If
              no  second beforeId argument is specified, the marker is placed at the beginning of
              the display list.  This command can be used to control how  markers  are  displayed
              since markers are drawn in the order of this display list.

       pathName marker bind tagName ?sequence?  ?command?
              Associates  command  with  tagName  such  that whenever the event sequence given by
              sequence occurs for a marker with this tag, command will be invoked.  The syntax is
              similar  to  the bind command except that it operates on graph markers, rather than
              widgets. See the bind manual  entry  for  complete  details  on  sequence  and  the
              substitutions performed on command before invoking it.

              If  all  arguments  are  specified  then  a  new  binding is created, replacing any
              existing binding for the same sequence and tagName.   If  the  first  character  of
              command  is  +  then command augments an existing binding rather than replacing it.
              If no command argument is provided  then  the  command  currently  associated  with
              tagName and sequence (it's an error occurs if there's no such binding) is returned.
              If both command and sequence are missing then a list of all the event sequences for
              which bindings have been defined for tagName.

       pathName marker cget option
              Returns  the  current  value  of  the  marker configuration option given by option.
              Option may be any option described below in the configure operation.

       pathName marker configure markerId ?option value?...
              Queries or modifies  the  configuration  options  for  markers.   If  option  isn't
              specified,  a  list  describing  the  current options for markerId is returned.  If
              option is specified, but not value, then a list describing option is returned.   If
              one  or  more  option and value pairs are specified, then for each pair, the marker
              option option is set to value.

              The following options are valid for all markers.  Each type of marker also has  its
              own type-specific options.  They are described in the sections below.

              -bindtags tagList
                     Specifies the binding tags for the marker.  TagList is a list of binding tag
                     names.  The tags and their order will determine how events for  markers  are
                     handled.  Each tag in the list matching the current event sequence will have
                     its Tcl command executed.  Implicitly the name of the marker is  always  the
                     first tag in the list.  The default value is all.

              -coords coordList
                     Specifies  the  coordinates  of  the  marker.   CoordList is a list of graph
                     coordinates.  The number of coordinates required is dependent on the type of
                     marker.   Text,  image, and window markers need only two coordinates (an X-Y
                     coordinate).   Bitmap markers can take either two or  four  coordinates  (if
                     four,  they represent the corners of the bitmap). Line markers need at least
                     four coordinates, polygons at least six.  If coordList  is  "",  the  marker
                     will not be displayed.  The default is "".

              -element elemName
                     Links the marker with the element elemName.  The marker is drawn only if the
                     element is also currently displayed (see the element's show operation).   If
                     elemName is "", the marker is always drawn.  The default is "".

              -hide boolean
                     Indicates whether the marker is drawn. If boolean is true, the marker is not
                     drawn.  The default is no.

              -mapx xAxis
                     Specifies the X-axis to map the marker's X-coordinates onto.  XAxis must the
                     name of an axis.  The default is x.

              -mapy yAxis
                     Specifies the Y-axis to map the marker's Y-coordinates onto.  YAxis must the
                     name of an axis.  The default is y.

              -name markerId
                     Changes the identifier for the marker.   The  identifier  markerId  can  not
                     already  be  used  by  another  marker.  If this option isn't specified, the
                     marker's name is uniquely generated.

              -under boolean
                     Indicates whether the marker is drawn below/above data elements.  If boolean
                     is  true,  the  marker is be drawn underneath the data elements.  Otherwise,
                     the marker is drawn on top of the element.  The default is 0.

              -xoffset pixels
                     Specifies a screen distance to offset the marker horizontally.  Pixels is  a
                     valid screen distance, such as 2 or 1.2i.  The default is 0.

              -yoffset pixels
                     Specifies  a  screen distance to offset the markers vertically.  Pixels is a
                     valid screen distance, such as 2 or 1.2i.  The default is 0.

              Marker configuration options may also be set by the option command.   The  resource
              class  is either BitmapMarker,  ImageMarker, LineMarker, PolygonMarker, TextMarker,
              or WindowMarker, depending on the type of marker.  The resource name is the name of
              the marker.

                     option add *Barchart.TextMarker.Foreground white
                     option add *Barchart.BitmapMarker.Foreground white
                     option add *Barchart.m1.Background     blue

       pathName marker create type ?option value?...
              Creates  a  marker  of  the  selected  type. Type may be either text, line, bitmap,
              image, polygon, or window.  This command returns the marker identifier, used as the
              markerId  argument  in  the  other marker-related commands.  If the -name option is
              used, this overrides the normal marker identifier.  If the name provided is already
              used for another marker, the new marker will replace the old.

       pathName marker delete ?name?...
              Removes  one  of more markers.  The graph will automatically be redrawn without the
              marker..

       pathName marker exists markerId
              Returns 1 if the marker markerId exists and 0 otherwise.

       pathName marker names ?pattern?
              Returns the names of all the markers that currently exist.  If pattern is supplied,
              only those markers whose names match it will be returned.

       pathName marker type markerId
              Returns  the  type  of  the  marker  given  by  markerId, such as line or text.  If
              markerId is not a valid a marker identifier, "" is returned.

   BITMAP MARKERS
       A bitmap marker displays a bitmap.  The size of the bitmap is controlled by the number  of
       coordinates  specified.   If  two  coordinates,  they specify the position of the top-left
       corner of the  bitmap.   The  bitmap  retains  its  normal  width  and  height.   If  four
       coordinates,  the  first  and  second  pairs  of  coordinates represent the corners of the
       bitmap.  The bitmap will be stretched or reduced as necessary to  fit  into  the  bounding
       rectangle.

       Bitmap markers are created with the marker's create operation in the form: pathName marker
       create bitmap ?option value?...  There  may  be  many  option-value  pairs,  each  sets  a
       configuration  options for the marker.  These same option-value pairs may be used with the
       marker's configure operation.

       The following options are specific to bitmap markers:

       -background color
              Same as the -fill option.

       -bitmap bitmap
              Specifies the bitmap to be displayed.  If bitmap is "",  the  marker  will  not  be
              displayed.  The default is "".

       -fill color
              Sets  the  background  color  of  the  bitmap.   If  color  is the empty string, no
              background will be transparent.  The default background color is "".

       -foreground color
              Same as the -outline option.

       -mask mask
              Specifies a mask for the bitmap to be displayed. This  mask  is  a  bitmap  itself,
              denoting  the pixels that are transparent.  If mask is "", all pixels of the bitmap
              will be drawn.  The default is "".

       -outline color
              Sets the foreground color of the bitmap. The default value is black.

       -rotate theta
              Sets the rotation of the bitmap.  Theta is a real number representing the angle  of
              rotation  in degrees.  The marker is first rotated and then placed according to its
              anchor position.  The default rotation is 0.0.

   IMAGE MARKERS
       A image marker displays an image.  Image markers are  created  with  the  marker's  create
       operation  in  the form: pathName marker create image ?option value?...  There may be many
       option-value pairs,  each  sets  a  configuration  option  for  the  marker.   These  same
       option-value pairs may be used with the marker's configure operation.

       The following options are specific to image markers:

       -anchor anchor
              Anchor  tells  how  to position the image relative to the positioning point for the
              image. For example, if anchor is center then the image is centered  on  the  point;
              if  anchor  is n then the image will be drawn such that the top center point of the
              rectangular region occupied by the image will be at the  positioning  point.   This
              option defaults to center.

       -image image
              Specifies  the  image  to  be drawn.  If image is "", the marker will not be drawn.
              The default is "".

   LINE MARKERS
       A line marker displays one or more connected line segments.  Line markers are created with
       marker's  create  operation  in  the  form:  pathName marker create line ?option value?...
       There may be many option-value pairs, each sets a configuration  option  for  the  marker.
       These same option-value pairs may be used with the marker's configure operation.

       The following options are specific to line markers:

       -dashes dashList
              Sets  the  dash  style  of  the  line.  DashList is a list of up to 11 numbers that
              alternately represent the lengths of the dashes and gaps on the line.  Each  number
              must be between 1 and 255.  If dashList is "", the marker line will be solid.

       -fill color
              Sets  the background color of the line.  This color is used with striped lines (see
              the -fdashes option).  If color is the empty string, no background color  is  drawn
              (the line will be dashed, not striped).  The default background color is "".

       -linewidth pixels
              Sets the width of the lines.  The default width is 0.

       -outline color
              Sets the foreground color of the line. The default value is black.

       -stipple bitmap
              Specifies  a  stipple  pattern  used  to  draw  the line, rather than a solid line.
              Bitmap specifies a bitmap to use as the stipple pattern.  If bitmap is "", then the
              line is drawn in a solid fashion. The default is "".

   POLYGON MARKERS
       A  polygon  marker  displays  a  closed  region  described  as  two or more connected line
       segments.  It is assumed the first and last points are  connected.   Polygon  markers  are
       created  using  the  marker  create  operation in the form: pathName marker create polygon
       ?option value?...  There may be many option-value pairs, each sets a configuration  option
       for  the  marker.   These  same  option-value  pairs may be used with the marker configure
       command to change the marker's configuration.  The following  options  are  supported  for
       polygon markers:

       -dashes dashList
              Sets  the  dash style of the outline of the polygon. DashList is a list of up to 11
              numbers that alternately represent the lengths  of  the  dashes  and  gaps  on  the
              outline.   Each  number  must  be between 1 and 255. If dashList is "", the outline
              will be a solid line.

       -fill color
              Sets the fill color of the polygon.  If color is  "",  then  the  interior  of  the
              polygon is transparent.  The default is white.

       -linewidth pixels
              Sets  the  width  of  the  outline of the polygon. If pixels is zero, no outline is
              drawn. The default is 0.

       -outline color
              Sets the color of the outline of the polygon.  If the polygon is stippled (see  the
              -stipple  option),  then  this represents the foreground color of the stipple.  The
              default is black.

       -stipple bitmap
              Specifies that the polygon should be drawn with a stippled pattern  rather  than  a
              solid color. Bitmap specifies a bitmap to use as the stipple pattern.  If bitmap is
              "", then the polygon is filled with a solid color (if the  -fill  option  is  set).
              The default is "".

   TEXT MARKERS
       A  text  marker  displays  a  string of characters on one or more lines of text.  Embedded
       newlines cause line breaks.  They may be used to annotate  regions  of  the  graph.   Text
       markers  are  created  with  the create operation in the form: pathName marker create text
       ?option value?...  There may be many option-value pairs, each sets a configuration  option
       for  the  text  marker.   These  same  option-value  pairs  may  be used with the marker's
       configure operation.

       The following options are specific to text markers:

       -anchor anchor
              Anchor tells how to position the text relative to the  positioning  point  for  the
              text.  For  example, if anchor is center then the text is centered on the point; if
              anchor is n then the text will be drawn such that  the  top  center  point  of  the
              rectangular  region  occupied  by  the text will be at the positioning point.  This
              default is center.

       -background color
              Same as the -fill option.

       -font fontName
              Specifies the font of the text.  The default is *-Helvetica-Bold-R-Normal-*-120-*.

       -fill color
              Sets the background color of the text.  If color is the empty string, no background
              will be transparent.  The default background color is "".

       -foreground color
              Same as the -outline option.

       -justify justify
              Specifies  how  the  text  should  be justified.  This matters only when the marker
              contains more than one line of text. Justify must be left, right, or  center.   The
              default is center.

       -outline color
              Sets the color of the text. The default value is black.

       -padx pad
              Sets the padding to the left and right exteriors of the text.  Pad can be a list of
              one or two screen distances.  If pad has two elements, the left side of the text is
              padded by the first distance and the right side by the second.  If pad has just one
              distance, both the left and right sides are padded evenly.  The default is 4.

       -pady pad
              Sets the padding above and below the text.  Pad can be a list of one or two  screen
              distances.  If pad has two elements, the area above the text is padded by the first
              distance and the area below by the second.  If pad is just one distance,  both  the
              top and bottom areas are padded evenly.  The default is 4.

       -rotate theta
              Specifies  the  number  of  degrees  to  rotate  the  text.  Theta is a real number
              representing the angle of rotation.  The marker is first rotated along  its  center
              and is then drawn according to its anchor position. The default is 0.0.

       -text text
              Specifies  the  text  of  the  marker.   The exact way the text is displayed may be
              affected by other options such as -anchor or -rotate.

   WINDOW MARKERS
       A window marker displays a widget at a given position.  Window markers  are  created  with
       the marker's create operation in the form: pathName marker create window ?option value?...
       There may be many option-value pairs, each sets a configuration  option  for  the  marker.
       These same option-value pairs may be used with the marker's configure command.

       The following options are specific to window markers:

       -anchor anchor
              Anchor  tells  how to position the widget relative to the positioning point for the
              widget. For example, if anchor is center then the widget is centered on the  point;
              if  anchor is n then the widget will be displayed such that the top center point of
              the rectangular region occupied by the widget will be  at  the  positioning  point.
              This option defaults to center.

       -height pixels
              Specifies  the  height  to  assign  to  the  marker's window.  If this option isn't
              specified, or if it is specified as "", then the window is  given  whatever  height
              the widget requests internally.

       -width pixels
              Specifies  the  width  to  assign  to  the  marker's  window.  If this option isn't
              specified, or if it is specified as "", then the window is given whatever width the
              widget requests internally.

       -window pathName
              Specifies  the  widget  to be managed by the barchart.  PathName must be a child of
              the barchart widget.

GRAPH COMPONENT BINDINGS

       Specific barchart components, such as elements, markers and legend  entries,  can  have  a
       command  trigger  when event occurs in them, much like canvas items in Tk's canvas widget.
       Not all event sequences are valid.  The only binding events  that  may  be  specified  are
       those  related  to  the mouse and keyboard (such as Enter, Leave, ButtonPress, Motion, and
       KeyPress).

       Only one element or marker can be picked during an event.  This means, that if  the  mouse
       is  directly  over both an element and a marker, only the uppermost component is selected.
       This isn't true for legend entries.  Both a  legend  entry  and  an  element  (or  marker)
       binding commands will be invoked if both items are picked.

       It  is  possible for multiple bindings to match a particular event.  This could occur, for
       example, if one binding is associated with the element name and another is associated with
       one  of  the  element's  tags  (see  the  -bindtags option).  When this occurs, all of the
       matching bindings are invoked.  A binding associated with  the  element  name  is  invoked
       first,  followed by one binding for each of the element's bindtags.  If there are multiple
       matching bindings for a single tag, then only the most specific  binding  is  invoked.   A
       continue  command  in  a  binding  script  terminates  that  script,  and  a break command
       terminates that script and skips any remaining scripts for the event, just as for the bind
       command.

       The  -bindtags  option  for  these  components  controls  addition  tag names which can be
       matched.  Implicitly elements and markers always have tags matching their names.   Setting
       the value of the -bindtags option doesn't change this.

C LANGUAGE API

       You can manipulate data elements from the C language.  There may be situations where it is
       too expensive to translate the data values from ASCII strings.  Or you might want to  read
       data in a special file format.

       Data  can  manipulated  from  the  C language using BLT vectors.  You specify the X-Y data
       coordinates of an element as vectors and manipulate the vector from C.  The barchart  will
       be redrawn automatically after the vectors are updated.

       From Tcl, create the vectors and configure the element to use them.

              vector X Y
              .g element configure line1 -xdata X -ydata Y

       To  set  data  points  from  C,  you  pass  the  values  as  arrays  of  doubles using the
       Blt_ResetVector call.  The vector is reset with the new data and at the  next  idle  point
       (when Tk re-enters its event loop), the graph will be redrawn automatically.

              #include <tcl.h>
              #include <blt.h>

              register int i;
              Blt_Vector *xVec, *yVec;
              double x[50], y[50];

              /* Get the BLT vectors "X" and "Y" (created above from Tcl) */
              if ((Blt_GetVector(interp, "X", 50, &xVec) != TCL_OK) ||
                  (Blt_GetVector(interp, "Y", 50, &yVec) != TCL_OK)) {
                  return TCL_ERROR;
              }

              for (i = 0; i < 50; i++) {
                  x[i] = i * 0.02;
                  y[i] = sin(x[i]);
              }

              /* Put the data into BLT vectors */
              if ((Blt_ResetVector(xVec, x, 50, 50, TCL_VOLATILE) != TCL_OK) ||
                  (Blt_ResetVector(yVec, y, 50, 50, TCL_VOLATILE) != TCL_OK)) {
                 return TCL_ERROR;
              }

       See the vector manual page for more details.

SPEED TIPS

       There  may  be  cases  where  the  bar  chart  needs to be drawn and updated as quickly as
       possible.  If drawing speed becomes a big problem,  here  are  a  few  tips  to  speed  up
       displays.

       · Try  to  minimize  the  number of data points.  The more data points looked at, the more
         work the bar chart must do.

       · If your data is generated as floating point values, the time  required  to  convert  the
         data values to and from ASCII strings can be significant, especially when there any many
         data points.  You can avoid the redundant string-to-decimal conversions using the C  API
         to BLT vectors.

       · Don't stipple or dash the element.  Solid bars are much faster.

       · If  you  update  data  elements frequently, try turning off the widget's -bufferelements
         option.  When the bar chart is first displayed, it draws data elements into an  internal
         pixmap.   The  pixmap  acts  as  a cache, so that when the bar chart needs to be redrawn
         again, and the data elements or coordinate axes haven't changed, the  pixmap  is  simply
         copied to the screen.  This is especially useful when you are using markers to highlight
         points and regions on the bar chart.  But  if  the  bar  chart  is  updated  frequently,
         changing either the element data or coordinate axes, the buffering becomes redundant.

LIMITATIONS

       Auto-scale  routines  do  not  use requested min/max limits as boundaries when the axis is
       logarithmically scaled.

       The PostScript output generated for polygons with more than 1500  points  may  exceed  the
       limits  of  some printers (See PostScript Language Reference Manual, page 568).  The work-
       around is to break the polygon into separate pieces.

KEYWORDS

       bar chart, widget