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NAME

       d.vect.thematic  - Displays a thematic vector map in the active graphics frame.

KEYWORDS

       display, cartography, choropleth map, legend

SYNOPSIS

       d.vect.thematic
       d.vect.thematic --help
       d.vect.thematic [-len] map=name  [layer=string]  column=name  [breaks=string[,string,...]]
       [algorithm=string]    [nclasses=integer]   colors=string[,string,...]    [where=sql_query]
       [boundary_width=integer]     [boundary_color=name]     [legendfile=name]     [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -l
           Create legend information and send to stdout

       -e
           When printing legend info,  include  extended  statistical  info  from  classification
           algorithm

       -n
           Do not draw map, only output the legend

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name [required]
           Name of vector map
           Or data source for direct OGR access

       layer=string
           Layer number or name
           Layer number. If -1, all layers are displayed.
           Default: 1

       column=name [required]
           Name of attribute column to be classified

       breaks=string[,string,...]
           Class breaks, without minimum and maximum

       algorithm=string
           Algorithm to use for classification
           Options: int, std, qua, equ, dis
           int: simple intervals
           std: standard deviations
           qua: quantiles
           equ: equiprobable (normal distribution)

       nclasses=integer
           Number of classes to define

       colors=string[,string,...] [required]
           Colors (one per class)

       where=sql_query
           WHERE conditions of SQL statement without ’where’ keyword
           Example: income < 1000 and inhab >= 10000

       boundary_width=integer
           Boundary width
           Default: 0

       boundary_color=name
           Boundary color
           Either a standard color name or R:G:B triplet
           Default: black

       legendfile=name
           File in which to save d.graph instructions for legend display

DESCRIPTION

       d.vect.thematic  draws  thematic choropleth vector maps based on an attribute column or an
       expression involving several columns.  It takes a list  of  class  breaks  (excluding  the
       minimum  and  maximum  values) and a list of colors to apply to the classes (has to be the
       number of class breaks + 1).

       Instead of a list of class breaks, the user can also chose a classification algorithm  and
       a  number  of classes (nbclasses). See the v.class for more information on these different
       algorithms.

       Important note: The module currently  supports  only  area  vector  type.  For  displaying
       thematic   choropleth   vector   maps   of   other  types  (points,  lines)  can  be  used
       d.vect.thematic2 available in AddOns via g.extension.

NOTES

       The -l flag instructs the module to print legend information (class  min  |  class  max  |
       number  of  observations  in class | color) to standard output for futher use in graphical
       software.  When combined with the -e flag, the legend information will  be  extended  with
       some additional statistical information. If the -n flag is set, the module will only print
       the legend information without drawing the map. If the user gives a legendfile, the module
       will write d.graph instructions for painting a legend into that file.

EXAMPLES

   Thematic map with classes
       d.vect.thematic -l map=communes3 column=pop \
         breaks=111393.250000,222785.500000,334177.750000 \
         colors="255:0:0,0:255:0,0:0:255,0,0,0"

   Thematic map with calculated class breaks
       The  following  example  uses a calculated attribute (density = pop/area) and the standard
       deviation algorithm to calculate class breaks for 5 classes:
       d.vect.thematic -l map=communes2 column=pop/area algorithm=std \
         nbclasses=5 colors="0:0:255,50:100:255,255:100:50,255:0:0,156:0:0"
       To actually draw the legend for the polygons in the graphical display, the procedure is:
       # first save legend instructions to a file
       d.vect.thematic -n map=communes2 column=pop/area algorithm=std \
         nbclasses=5 colors="0:0:255,50:100:255,255:100:50,255:0:0,156:0:0" \
         legendfile=legend_pop_dens
       # open a monitor
       d.mon wx0
       # draw the map
       d.vect.thematic map=communes2 column=pop/area algorithm=std \
         nbclasses=5 colors="0:0:255,50:100:255,255:100:50,255:0:0,156:0:0"
       # draw the legend
       d.graph input=legend_pop_dens
       In order to further enhance this legend, edit the legend file accordingly  and  rerun  the
       process.

   Thematic map with calculated class breaks
       Example for the North Carolina sample dataset, colorizing polygons by area size:
       # first save legend instructions to a file
       d.vect.thematic -n map=geology column=SHAPE_area algorithm=int nclasses=6 \
        colors=215:48:39,252:141:89,254:224:139,217:239:139,145:207:96,26:152:80 \
        legendfile=geology.leg
       # open the graphical display
       d.mon wx0
       # draw outline of polygons
       d.vect map=geology type=boundary
       # draw color fill
       d.vect.thematic map=geology column=SHAPE_area algorithm=int nclasses=6 \
        colors="215:48:39,252:141:89,254:224:139,217:239:139,145:207:96,26:152:80" \
       # draw legend
       d.graph input=geology.leg
       Thematic map of area sizes

SEE ALSO

        v.class, d.vect, d.graph, v.univar

       Check also Python module from AddOns: d.vect.thematic2

AUTHOR

       Moritz Lennert

       Last changed: $Date: 2015-08-11 23:07:09 +0200 (Tue, 11 Aug 2015) $

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