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.

EXAMPLE

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

SEE ALSO

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

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

AUTHOR

Moritz Lennert

Last changed: $Date$