Provided by: libncarg-dev_6.3.0-6build1_amd64 bug

NAME

       Streamlines_params - This document briefly describes all Streamlines internal parameters.

DESCRIPTION

       Parameter descriptions follow, in alphabetical order. Each description begins with a line
       giving the three-character mnemonic name of the parameter, the phrase for which the
       mnemonic stands, and the intrinsic type of the parameter.

       AGD - Arrow Placement Grid Increment - Integer
              This parameter allows you a degree of control over directional arrowhead spacing in
              the field flow plot.  Streamlines allows a maximum of one directional arrowhead for
              each grid box, where a grid box is the space between adjacent integer grid
              coordinates in the grid coordinate system along both dimensions. However,
              Streamlines actually places an arrowhead only if both lower grid indices, modulo
              the value of AGD, are equal to 0. If AGD is set to 2, for instance, Streamlines
              places an arrowhead on the first streamline to enter each grid box with even-
              numbered lower grid indices.

              If the transformation pipeline is everywhere linear from grid coordinate space to
              NDC space, then the spacing of the arrowheads should be more or less uniform over
              the field flow plot. However, if there is a non-linearity anywhere in the pipeline,
              the arrowheads will probably be more crowded in some areas than in others. The
              default value of AGD is 2.

       AMD - Arrow Head Minimum Distance - Real
              AMD allows you to specify, as a fraction of the viewport width, a minimum distance
              between adjacent directional arrowheads along a single streamline. If the data grid
              is transformed in such a way that adjacent grid cells become very close in NDC
              space, as for instance in many map projections near the poles, you can use this
              parameter to help reduce the otherwise cluttered appearance of these regions of the
              plot. Note that currently, whenever AMD has a positive value, the first arrowhead
              that would otherwise be drawn for each streamline is always eliminated. If AMD is
              less than or equal to 0.0, then no arrowheads are eliminated. The default value of
              AMD is 0.0.

       ARL - Arrow Head Length - Real
              ARL defines the length of each of the two lines used to create the directional
              arrow head. If the parameter GBS is set to 0, ARL has units "fraction of viewport
              width"; if GBS is set to 1, ARL has the units "fraction of grid box width".  The
              default value of ARL is 0.012 when GBS has the value 0 and 0.33 when GBS has the
              value 1. Setting GBS causes ARL to be reset to its appropriate default value.

       CDS - Critical Displacement Multiplier - Real
              CDS specifies the minimum amount the streamline must grow as a multiple of the
              basic differential step size each time the stream progress is checked in order for
              the streamline not to be terminated. The nominal differential step size is
              specified by DFM in NDC space, and the progress is checked each CKP iterations.
              Points of convergence or divergence typically cause stream growth to diminish and
              the streamline eventually to be terminated. The default value of CDS is 2.0,
              meaning that any time a streamline does not increase in length a minimum of 2.0*DFM
              in NDC over the previous check, it is discontinued and a new streamline is begun if
              possible.

       CKP - Check Progress Iteration Count - Integer
              The parameter CKP specifies the number of iterations through the streamline
              building loop between each check of the streamline growth. If the distance between
              current position of the streamline and the position saved at the time of the
              previous check is less than a minimum amount, defined as the value of CDS times the
              value of DFM in NDC space, then the current streamline is terminated and a new one
              begun if possible. The default value of CKP is 35.

       CKX - Check Crossover Iteration Count - Integer
              CKX specifies the number of iterations through the streamline building loop between
              checks for streamline crossover, that is, one streamline growing closer than a
              certain distance (as specified by the parameter SSP) to previously created
              streamline. A negative value of CKX causes Streamlines to check for crossover only
              when a new grid box is entered. At each crossover check, the current streamline
              position is compared with a sampling of previous streamline positions retained in
              an internal circular list. This list is currently fixed to a length of 750. Since
              up to this number of comparisons are performed at each crossover check, the
              frequency with which these checks are performed can have a noticeable impact on
              performance. By default, CKX has the value -99, causing Streamlines to check for
              crossover only on entrance to a new grid box.

       CYK - Cyclical Data Flag - Integer
              Use this parameter to specify that the data in the vector field arrays is cyclical:
              that is, it repeats with a period of M-1 (M, the input parameter to STINIT) along
              the first dimensional axis. If the flag is set on, Streamlines checks to see if the
              field data meet certain criteria. If they do, an internal cyclical flag is set,
              causing the normalized vector interpolation routines to consider data from the
              opposite ends of the dataset when interpolating near the first dimensional dataset
              boundaries. If the criteria are not met, Streamlines sets an error flag,
              retrievable by the user through the parameter ERR. Processing, however, continues
              without interruption, except that Streamlines now interpolates (as it would
              ordinarily) near the first dimensional end points without consideration of data at
              the opposite end. The data must pass the following test in order to be deemed
              cyclical: for each subscript value along the second dimensional axis, the first
              element and the last element along the first dimensional axis must be identical. A
              value of 0 for CYK means that the data is to be considered non-cyclical; any other
              value means that Streamlines should test for the cyclical condition.  You must
              initialize Streamlines with a call to STINIT after modifying this parameter. The
              default value of CYK is 0.

       CPM - Compatibility Mode - Integer
              Controls the degree of compatibility between versions of the Streamlines utility
              prior to NCAR Graphics 3.2 and the current version. You can independently control
              three behaviors using the nine settings provided:

              ·      use of STRMLN input parameters;

              ·      use of variables contained in the common blocks STR02 and STR03;

              ·      use of the old coordinate mapping routines, FX and FY.

              Note, however, that when using the Version 3.2 entry points STINIT and STREAM, only
              the third behavior option has any meaning.

              When CPM is set to 0, its default value, the Streamlines utility´s behavior varies
              depending on whether you access it through one of the pre-Version 3.2 entry points
              (STRMLN and EZSTRM), or through the STINIT/STREAM interface. Otherwise, positive
              values result in invocation of the older coordinate mapping routines (FX and FY).
              Negative values cause the Version 3.2 mapping routines to be used instead.  When
              using the pre-Version 3.2 interface only, odd values of CPM cause the data values
              in the common blocks, STR02 and STR03, to override corresponding values initialized
              in the Version 3.2 STDATA block data subroutine, or set by the user calling STSETx
              routines.  Values of CPM with absolute value less than or equal to two cause the
              NSET argument to STRMLN to take precedence over the SET parameter.

              Here is a table of the nine settings of CPM and their effect on the operation of
              the Streamlines utility:

              Value   Use FX and FY            Use STR02,STR03   Use NSET
              -----   -------------            ---------------   --------
              -4      no                       no                no
              -3      no                       yes               no
              -2      no                       no                yes
              -1      no                       yes               yes
              0       old - yes;new - no (*)   yes               yes
              1       yes                      yes               yes
              2       yes                      no                yes

              3       yes                      yes               no
              4       yes                      no                no

              (*) Old means EZSTRM or STRMLN entry point; new, STINIT/STREAM.  Only the first
              column is applicable to the behavior of the STINIT/STREAM interface. See the strmln
              man page for more detailed emulation information.

       DFM - Streamline Differential Magnitude
              DFM specifies the length of the differential magnitude step size used by
              Streamlines. If the parameter GBS is set to 0 DFM has units "fraction of viewport
              width"; if GBS is set to 1, DFM has the units "fraction of grid box width". When
              the Version 3.2 mapping routines are used, DFM directly affects processing time and
              the resulting plot precision. In general, smaller values of DFM cause Streamlines
              to take more, smaller steps in the construction of a streamline, resulting, within
              the limits of the processor´s floating point resolution, in longer execution times
              and a more precise plot.  Process memory requirements are not affected. If the
              compatibility mode parameter is set such that the older mapping routines, FX and
              FY, are invoked instead, DFM no longer has any effect on the plot, since in this
              case the step size is determined by the setting of the parameter VNL as a fraction
              of the grid box width. The default value of DFM is 0.02 when GBS has the value 0
              and 0.33 when GBS has the value 1. Setting GBS causes DFM to be reset to its
              appropriate default value.

       GBS - Grid-Based Spacing - Real
              The parameter GBS controls the interpretation of several parameters that play a
              critical role in the appearance of the streamline plot. These parameters are DFM,
              SSP, and ARL. When GBS has the value 0, the values of these parameters are treated
              as having units of "fraction of viewport width". If GBS has the value 1, the values
              are treated as having the units of "fraction of grid box width". Whenever you set
              GBS, the three affected parameters are reset to default values appropriate to the
              units; therefore you must set GBS prior to setting any non-default values for DFM,
              SSP, or ARL. You may find that using the grid-based spacing method causes
              Streamlines to adapt more gracefully to variations in the density of the data grid.
              Currently, the default value of GBS is 0; however, in the next release this may
              change.

       LWD - Streamline Linewidth - Real
              LWD controls the linewidth used to draw the streamlines.  Note that since the
              linewidth in NCAR Graphics is always calculated relative to a unit linewidth that
              is dependent on the output device, you may need to adjust the linewidth value
              depending on the output conditions to obtain a pleasing plot. LWD affects the
              linewidth of the directional arrowheads as well as the streamlines themselves. The
              arrowhead length also increases somewhat when the linewidth is greater than the
              default. However, the arrowhead length parameter still affects the length. The
              default is 1.0, specifying a device-dependent minimum linewidth.

       MAP - Map Transformation Code - Integer
              MAP defines the mapping transformation between the data and user coordinate space.
              For more information on coordinate mapping transformations see the stuixy, stumxy,
              and stumta man pages, as well as the description of the transformation type
              parameter, TRT.  Three MAP parameter codes are reserved for pre-defined
              transformations, as follows:

              Value          Mapping transformation

              0 (default)    Identity transformation between data and user coordinates: array
                             indices of U and V are linearly related to user coordinates.  Note
                             however that a non-linear transformation is still possible from user
                             to NDC coordinates.

              1              Ezmap transformation: first dimension indices of U and V are
                             linearly related to longitude; second dimension indices are linearly
                             related to latitude.

              2              Polar to rectangular transformation: first dimension indices of U
                             and V are linearly related to the radius; second dimension indices
                             are linearly related to the angle in degrees.

              If MAP has any other value, Streamlines invokes the user-modifiable subroutines,
              STUMXY, STUIXY, and STUMTA to perform the mapping. The default version of these
              routines simply performs an identity mapping.  Note that, while the Streamlines
              utility does not actually prohibit the practice, you are advised not to use
              negative integers for user-defined mappings, since other utilities in the NCAR
              Graphics toolkit attach a special meaning to negative mapping codes.

              For all the predefined mappings, the linear relationship between the grid array
              indices and the data coordinate system is established using the four parameters,
              XC1, XCM, YC1, and YCN. The X parameters define a mapping for the first and last
              indices of the first dimension of the data arrays, and the Y parameters do the same
              for the second dimension. If MAP is set to a value of one, you need to be careful
              to ensure that the SET parameter is given a value of zero, since the Ezmap routines
              require a specific user coordinate space for each projection type, and internally
              call the SET routine to define the user to NDC mapping.  Otherwise, you may choose
              whether or not to issue a SET call prior to calling STINIT, modifying the value of
              SET as required. See the description of the parameter, TRT, and the man pages,
              stumxy, stuixy, and stumta for more information.

       MSK - Mask To Area Map Flag - Integer
              Use this parameter to control masking of streamlines to an existing area map
              created by routines in the Areas utility.  When MSK is greater than 0, masking is
              enabled and an area map must be set up before calling STREAM. The area map array
              and, in addition, the name of a user-definable masked drawing routine, must be
              passed as input parameters to STREAM. There are two states for the MSK parameter,
              as follows:

              Value          Effect

              <= 0 (default) No streamline masking.

              >0             The subroutine ARDRLN is called internally to decompose the
                             streamlines into segments contained entirely within a single area
                             group. ARDRLN calls the user-definable masked drawing subroutine.

              See the man page, stumsl, for further information on the user-definable masked
              drawing subroutine.

       PLR - Polar Input Mode - Integer
              When PLR is greater than zero, the vector component arrays are considered to
              contain the field data in polar coordinate form: the U array is treated as
              containing the vector magnitude and the V array as containing the vector angle. Be
              careful not to confuse the PLR parameter with the MAP parameter polar coordinate
              mode. The MAP parameter relates to the location of the vector, not its value. Here
              is a table of values for PLR:

              Value          Meaning

              0 (default)    U and V arrays contain data in cartesian component form.

              1              U array contains vector magnitudes; V array contains vector angles
                             in degrees.

              2              U array contain vector magnitudes; V array contains vector angles in
                             radians.

              You must initialize Streamlines with a call to STINIT after modifying this
              parameter.

       SET - SET Call Flag - Integer
              Give SET the value 0 to inhibit the SET call STINIT performs by default. Arguments
              5-8 of a SET call made by the user must be consistent with the ranges of the user
              coordinates expected by Streamlines. This is determined by the mapping from grid to
              data coordinates as specified by the values of the parameters XC1, XCM, YC1, YCN,
              and also by the mapping from data to user coordinates established by the MAP
              parameter. You must initialize Streamlines with a call to STINIT after modifying
              this parameter. The default value of SET is 1.

       SGD - Stream Starting Grid Increment - Integer
              This parameter gives you a degree of control over the number and density of
              streamlines in the field flow plot.  The Streamlines utility never begins a
              streamline in any grid box that has previously had a streamline pass through it,
              where a grid box is defined as the space between adjacent integer grid coordinates
              in the grid coordinate system along both dimensions. By setting SGD to a value
              greater than 1, you can reduce the number of grid boxes initially eligible for
              starting a streamline. A grid box is considered initially eligible for starting a
              streamline only if both the lesser indices that establish the grid box, modulo the
              value of SGD, equal 0. If SGD is set to 2, for instance, every grid box with even-
              numbered lower grid indices would be initially eligible for starting a streamline.
              As the streamlines grow and pass through grid boxes that were initially eligible,
              these boxes too are marked ineligible, further reducing the boxes where a stream
              can be started.

              If the transformation pipeline is everywhere linear from grid coordinate space to
              NDC space, then this scheme for starting streamlines usually produces a more or
              less uniform spacing of the streamlines over the field flow plot. However, if there
              are non-linear transforms anywhere in the pipeline, the streamlines will probably
              be more crowded in some areas than in others. Future enhancements to the
              Streamlines utility are expected to address this issue, and also perhaps to provide
              options for intentional non-uniform spacing based on flow intensity. The default
              value of SGD is 2.

       SSP - Streamline Spacing Value - Real
              The streamline spacing parameter establishes the minimum distance a streamline in
              progress is allowed to approach existing streamlines before being terminated. If
              the parameter GBS is set to 0, SSP has units "fraction of viewport width"; if GBS
              is set to 1, SSP has the units "fraction of grid box width". In general, within
              either system of units, larger values of SSP increase the distance between
              streamlines, and have a tendency to create more, but shorter stream lines. The
              spacing is only checked at intervals, so streamlines sometimes approach closer than
              the specified distance. The checking frequency is adjustable using the streamline
              crossover checking parameter, CKX. The streamline starting grid increment
              parameter, SGD, also affects the overall streamline density. The default value of
              SSP is 0.015 when GBS has the value 0 and 0.5 when GBS has the value 1. Setting GBS
              causes SSP to be reset to its appropriate default value.

       SST - Streamline Statistics Output Flag - Integer
              If SST is set to one, STREAM writes a summary of its operations to the default
              logical output unit, including the number of streamlines plotted and the total
              differential step count. Here is a sample of the output:

                 STREAM Statistics
                                 Streamlines plotted:  119
                       Total differential step count:  2903

              The differential step count actually counts the number of iterations through the
              main streamline construction loop, and can be used to help gauge the trade-offs
              between the increased processing time required for smaller differential step sizes
              and the resulting differences in plot quality.

       SVF - Special Value Flag - Integer
              The special value flag controls special value processing for the U and V vector
              component data arrays. Special values may appear in either the U or V array or in
              both of them. When any of the four points surrounding the current streamline end
              contain a special value, the streamline is terminated, and a new one started, if
              possible. Streamlines allows special value processing to be turned on or off, as
              follows:

              Value          Effect

              0 (default)    Neither the U nor the V array is examined for special values

              non 0          Whenever the streamline under construction enters a new grid box,
                             the U and V array values at each corner of the box are examined for
                             special values. The interpolation method parameter, TRP, is
                             overridden, causing Streamlines to use bi-linear interpolation only.

              The U and V special values are defined by setting parameters USV and VSV.
              Streamlines only uses bi-linear interpolation when special value processing is in
              effect, because the Bessel interpolation method quadruples the requirement for good
              data points (from 4 to 16) surrounding the current stream end point. You must
              initialize Streamlines with a call to STINIT after modifying this parameter.

       TRP - Interpolation Method - Integer
              Use TRP to control which of two interpolation methods Streamlines should use in
              determining the normalized flow components for each point in the streamline. The
              choices are as follows:

              Value          Interpolation Method

              0 (default)    Use the 16-point Bessel interpolation method where possible;
                             otherwise, near the data set boundaries use 12, 9 or 4 point
                             interpolation methods, depending on the situation.

              non 0          Use 4-point bi-linear interpolation at all points.

              Note that Streamlines forces use of the 4-point bi-linear interpolation method if
              the SVF parameter is set to turn on special value processing.

       TRT - Transformation Type - Integer
              The transformation type parameter, TRT, qualifies the mapping transformation
              specified by the MAP parameters, as follows:

              Value          Effect

              -1             Direction, magnitude, and location are all transformed. This option
                             is not currently supported by any of the pre-defined coordinate
                             system mappings.

              0              Only location is transformed

              1 (default)    Direction and location are transformed

              This parameter allows you to distinguish between a system that provides a mapping
              of location only into an essentially cartesian space, and one in which the space
              itself mapped. To understand the difference, using polar coordinates as an example,
              imagine a set of wind speed monitoring units located on a radial grid around some
              central point such as an airport control tower. Each unit´s position is defined in
              terms of its distance from the tower and its angular direction from due east.
              However, the data collected by each monitoring unit is represented as conventional
              eastward and northward wind components.  Assuming the towers´s location is at a
              moderate latitude, and the monitoring units are reasonably ´local´, this is an
              example of mapping a radially defined location into a nearly cartesian space (i.e.
              if the northward components were all set to 0.0, the streamlines defined by the
              eastward components would all be parallel straight lines.  One would set MAP to two
              (for the polar transformation) and TRT to zero to model this data on a plot
              generated by the Streamlines utility.

              On the other hand, picture a set of wind data, again given as eastward and
              northward wind components, but this time the center of the polar map is actually
              one of the earth´s poles. In this case, the eastward components do not point in a
              single direction; instead they outline a series of concentric circles around the
              pole. This is a space mapping transformation: one would again set MAP to two, but
              TRT would be set to one to transform both direction and location.

              Changing the setting of this parameter affects the end results only when a non-
              uniform non-linear mapping occurs at some point in the transformation pipeline. For
              this discussion a uniform linear transformation is defined as one which satisfies
              the following equations:

                 x_out = x_offset + scale_constant * x_in
                 y_out = y_offset + scale_constant * y_in

              If scale_constant is not the same for both equations then the mapping is non-
              uniform.

              This option is currently implemented only for the pre-defined MAP parameter codes,
              0 and 2, the identity mapping and the polar coordinate mapping. However, it
              operates on a different stage of the transformation pipeline in each case. The
              polar mapping is non-linear from data to user coordinates. The identity mapping,
              even though necessarily linear over the data to user space mapping, can have a non-
              uniform mapping from user to NDC space, depending on the values given to the input
              parameters of the SET call. This will be the case whenever the LL input parameter
              specifies a logarithmic scaling or the viewport and the user coordinate boundaries
              do not have the same aspect ratio. Thus for a MAP value of 2, TRT affects the
              mapping between data and user space, whereas for MAP set to 0, TRT influences the
              mapping between user and NDC space.

       USV - U Array Special Value - Real
              USV is the U vector component array special value. It is a value outside the range
              of the normal data used to indicate that there is no valid data for this grid
              location. When the special value flag parameter, SVF, is non-zero, each time a
              streamline enters a new cell Streamlines will check for this special value in the U
              array at each of the four corners of the grid box. Anytime the special value is
              discovered, the current streamline is terminated and a new one started if possible.
              The default value given to USV is 1.0 * 10**12.

       VNL - Vector Normalization Value - Real
              The parameter, VNL, determines the value Streamlines uses to normalize the vector
              flow field, before beginning the streamline construction loop. When Streamlines is
              used with the pre-Version 3.2 mapping routines, FX and FY, the value of VNL
              determines the step size in the grid coordinate system used to construct the
              streamlines, as a fraction of the grid box size. When using FX and FY, smaller
              values of VNL result in smaller steps, more processing time and, within the limits
              of the processor´s floating point accuracy, a higher precision plot. However, if
              the mapping has non-linearities, the grid size does not remain constant over the
              transformation and the step size can vary greatly, resulting in discontinuities in
              certain areas of the plot.

              Streamline´s new mapping routines define the streamline differential magnitude in
              NDC space, ensuring a constant step size over the whole plot, notwithstanding any
              non-linearity in the transformation. When using the new mapping routines, the
              parameter DFM controls the step size in NDC space, and VNL is not adjustable by the
              user. (See the discussion of the compatibility mode parameter, CPM, for a
              discussion of how to switch between the old and new mapping routines.) The default
              value of VNL is 0.33.

       VPB - Viewport Bottom - Real
              The parameter VPB has an effect only when SET is non-zero, specifying that
              Streamlines should do the call to SET. It defines a minimum boundary value for the
              bottom edge of the viewport in NDC space, and is constrained to a value between 0.0
              and 1.0. It must be less than the value of the Viewport Top parameter, VPT. The
              actual value of the viewport bottom edge used in the plot may be greater than the
              value of VPB, depending on the setting of the Viewport Shape parameter, VPS.  You
              must initialize Streamlines with a call to STINIT after modifying this parameter.
              The default value of VPB is 0.05.

       VPL - Viewport Left - Real
              The parameter VPL has an effect only when SET is non-zero, specifying that
              Streamlines should do the call to SET. It defines a minimum boundary value for the
              left edge of the viewport in NDC space, and is constrained to a value between 0.0
              and 1.0. It must be less than the value of the Viewport Right parameter, VPR. The
              actual value of the viewport left edge used in the plot may be greater than the
              value of VPL, depending on the setting of the Viewport Shape parameter, VPS.  You
              must initialize Streamlines with a call to STINIT after modifying this parameter.
              The default value of VPL is 0.05.

       VPR - Viewport Right - Real
              The parameter VPR has an effect only when SET is non-zero, specifying that
              Streamlines should do the call to SET. It defines a maximum boundary value for the
              right edge of the viewport in NDC space, and is constrained to a value between 0.0
              and 1.0. It must be greater than the value of the Viewport Left parameter, VPL. The
              actual value of the viewport right edge used in the plot may be less than the value
              of VPR, depending on the setting of the Viewport Shape parameter, VPS.  You must
              initialize Streamlines with a call to STINIT after modifying this parameter.  The
              default value of VPR is 0.95.

       VPS - Viewport Shape - Real
              The parameter VPS has an effect only when SET is non-zero, specifying that
              Streamlines should do the call to SET; it defines the desired viewport shape, as
              follows:

              Value          Effect

              <0.0           The absolute value of VPS specifies the shape to use for the
                             viewport, as the ratio of the viewport width to its height,

              0.0            The viewport completely fills the area defined by the boundaries
                             specifiers, VPL, VPR, VPB, VPT

              >0.0,<1.0 (0.25,default)
                             Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape if MIN(R, 1.0/R)
                             is greater than VPS. Otherwise determine the shape as when VPS is
                             equal to 0.0.

              >= 1.0         Use R = (XCM-XC1)/(YCN-YC1) as the viewport shape if MAX(R, 1.0/R)
                             is less than VPS. Otherwise make the viewport a square.

              The viewport, whatever its final shape, is centered in, and made as large as
              possible in, the area specified by the parameters VPB, VPL, VPR, and VPT. You must
              initialize Streamlines with a call to STINIT after modifying this parameter.

       VPT - Viewport Top - Real
              The parameter VPT has an effect only when SET is non-zero, specifying that
              Streamlines should do the call to SET. It defines a maximum boundary value for the
              top edge of the viewport in NDC space, and is constrained to a value between 0.0
              and 1.0. It must be greater than the value of the Viewport Bottom parameter, VPB.
              The actual value of the viewport top edge used in the plot may be less than the
              value of VPT, depending on the setting of the Viewport Shape parameter, VPS.  You
              must initialize Streamlines with a call to STINIT after modifying this parameter.
              The default value of VPT is 0.95.

       VSV - V Array Special Value - Real
              VSV is the V vector component array special value. It is a value outside the range
              of the normal data used to indicate that there is no valid data for this grid
              location. When the special value flag parameter, SVF, is non-zero, each time a
              streamline enters a new cell Streamlines will check for this special value in the V
              array at each of the four corners of the grid box.  Anytime the special value is
              discovered, the current streamline is terminated and a new one started if possible.
              You must initialize Streamlines with a call to STINIT after modifying this
              parameter.  The default value given to VSV is 1.0 * 10**12.

       WDB - Window Bottom - Real
              When STINIT does the call to SET, the parameter WDB is used to determine argument
              number 7, the user Y coordinate at the bottom of the window. If WDB is not equal to
              WDT, WDB is used. If WDB is equal to WDT, but YC1 is not equal to YCN, then YC1 is
              used. Otherwise, the value 1.0 is used.  You must initialize Streamlines with a
              call to STINIT after modifying this parameter.  The default value of WDB is 0.0.

       WDL - Window Left - Real
              When STINIT the call to SET, the parameter WDL is used to determine argument number
              5, the user X coordinate at the left edge of the window. If WDL is not equal to
              WDR, WDL is used. If WDL is equal to WDR, but XC1 is not equal to XCM, then XC1 is
              used. Otherwise, the value 1.0 is used. You must initialize Streamlines with a call
              to STINIT after modifying this parameter.  The default value of WDL is 0.0.

       WDR - Window Right - Real
              When STINIT does the call to SET, the parameter WDR is used to determine argument
              number 6, the user X coordinate at the right edge of the window. If WDR is not
              equal to WDL, WDR is used. If WDR is equal to WDL, but XCM is not equal to XC1,
              then XCM is used.  Otherwise, the value of the STINIT input parameter, M, converted
              to a real, is used.  You must initialize Streamlines with a call to STINIT after
              modifying this parameter.  The default value of WDR is 0.0.

       WDT - Window Top - Real
              When STINIT does the call to SET, the parameter WDB is used to determine argument
              number 8, the user Y coordinate at the top of the window. If WDT is not equal to
              WDB, WDT is used. If WDT is equal to WDB, but YCN is not equal to YC1 then YCN is
              used. Otherwise, the value of the STINIT input parameter, N, converted to a real,
              is used.  You must initialize Streamlines with a call to STINIT after modifying
              this parameter.  The default value of WDT is 0.0.

       XC1 - X Coordinate at Index 1 - Real
              The parameter XC1 specifies the X coordinate value that corresponds to a value of 1
              for the first subscript of the U and V, vector field component arrays. Together
              with XCM, YC1, and YCN it establishes the mapping from grid coordinate space to
              data coordinate space. If XC1 is equal to XCM, 1.0 will be used. You must
              initialize Streamlines with a call to STINIT after modifying this parameter.  The
              default value of XC1 is 0.0.

       XCM - X Coordinate at Index M - Real
              The parameter XCM specifies the X coordinate value that corresponds to the value of
              the STINIT input parameter, M, for the first subscript of the U and V vector
              component arrays. Together with XC1, YC1, and YCN it establishes the mapping from
              grid coordinate space to data coordinate space. If XC1 is equal to XCM, the value
              of M, converted to a real, will be used. You must initialize Streamlines with a
              call to STINIT after modifying this parameter.  The default value of XCM is 0.0

       YC1 - Y Coordinate at Index 1 - Real
              The parameter YC1 specifies the Y coordinate value that corresponds to a value of 1
              for the first subscript of the U, V, vector component arrays as well as for the P
              scalar data array, if used. Together with YCN, XC1, and XCM it establishes the
              mapping from grid coordinate space to data coordinate space. If YC1 is equal to
              YCN, 1.0 will be used.  You must initialize Streamlines with a call to STINIT after
              modifying this parameter.  The default value of YC1 is 0.0

       YCN - Y Coordinate at Index N - Real
              The parameter YCN specifies the Y coordinate value that corresponds to the value of
              the STINIT input parameter, N, for the second subscript of the U and V vector
              component arrays as well as the P scalar data array, if used.  Together with YC1,
              XC1, and XCM it establishes the mapping from grid coordinate space to data
              coordinate space. If YC1 is equal to YCN, the value of N, converted to a real, will
              be used. You must initialize Streamlines with a call to STINIT after modifying this
              parameter.  The default value of YCN is 0.0

       ZFC - Zero Field Text Block Color - Integer
              If ZFC is greater or equal to zero, it specifies the GKS color index to use to
              color the Zero Field text block.  Otherwise the Zero Field text block is colored
              using the current GKS text color index. The default value of ZFC is -1.

       ZFP - Zero Field Text Block Positioning Mode - Integer
              The ZFP parameter allows you to justify, using any of the 9 standard justification
              modes, the Zero Field text block unit with respect to the position established by
              the parameters, ZFX and ZFY The position modes are supported as follows:

              Mode           Justification

              -4             The lower left corner of the text block is positioned at ZFX, ZFY.

              -3             The center of the bottom edge is positioned at ZFX, ZFY.

              -2             The lower right corner is positioned at ZFX, ZFY.

              -1             The center of the left edge is positioned at ZFX, ZFY.

              0 (default)    The text block is centered along both axes at ZFX, ZFY.

              1              The center of the right edge is positioned at ZFX, ZFY.

              2              The top left corner is positioned at ZFX, ZFY.

              3              The center of the top edge is positioned at ZFX, ZFY.

              4              The top right corner is positioned at ZFX, ZFY.

       ZFS - Zero Field Text Block Character Size - Real
              ZFS specifies the size of the characters used in the Zero Field graphics text block
              as a fraction of the viewport width. The default value is 0.033.

       ZFT - Zero Field Text String - Character* 36
              Use ZFT to modify the text of the Zero Field text block.  The Zero Field text block
              may appear whenever the U and V vector component arrays contain data such that all
              the grid points otherwise eligible for plotting contain zero magnitude vectors.
              Currently the string length is limited to 36 characters. Set ZFT to a single space
              (´ ´) to prevent the text from being displayed. The default value for the text is
              ´Zero Field´.

       ZFX - Zero Field Text Block X Coordinate - Real
              ZFX establishes the X coordinate of the Zero Field graphics text block as a
              fraction of the viewport width. Values less than 0.0 or greater than 1.0 are
              permissible and respectively represent regions to the left or right of the
              viewport. The actual position of the block relative to ZFX depends on the value
              assigned to the Zero Field Positioning Mode parameter, ZFP. The default value is
              0.5.

       ZFY - Zero Field Text Block Y Coordinate - Real
              ZFY establishes the Y coordinate of the minimum vector graphics text block as a
              fraction of the viewport height.  Values less than 0.0 or greater than 1.0 are
              permissible and respectively represent regions below and above the viewport. The
              actual position of the block relative to ZFY depends on the value assigned to the
              Zero Field Positioning Mode parameter, ZFP. The default value is 0.5.

SEE ALSO

       Online: stgetc, stgeti, stgetr, stinit, stream, streamlines, strset, stsetc, stseti,
       stsetr, stuixy, stumsl, stumta, stumxy, ncarg_cbind.

       Hardcopy: NCAR Graphics Fundamentals, UNIX Version

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.