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
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.
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.
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"
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.
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
v.class,
d.vect,
d.graph,
v.univar
Check also Python module from
AddOns: d.vect.thematic2
Moritz Lennert
Last changed: $Date: 2015-08-11 23:07:09 +0200 (Tue, 11 Aug 2015) $
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GRASS Development Team,
GRASS GIS 7.0.3 Reference Manual