d.vect.thematic.1grass man page

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) $

Main index | Display index | Topics index | Keywords index | Full index

© 2003-2016 GRASS Development Team, GRASS GIS 7.0.4 Reference Manual

Info

GRASS 7.0.4 Grass User's Manual