[GRASS-dev] vector symbology

Hamish hamish_nospam at yahoo.com
Thu Nov 16 17:39:55 EST 2006

Agata Gie³dowska wrote:
> I'm a new user of GRASS and I struggle with some options that I've
> learned with ArcGIS and are not easy to find or do not exist here.
> How can I set the symbology to a vector map to display map by
> attributes (different columns - one at a time) with the same colours
> for the same class/value/category?
> Example: I have a layer of soil map and want to display it by map unit
> - so that the same units have the same colour and not just a random
> selection of colours assigned automaticaly for polygons.
> Or other time same map displayed by soil type (other column within
> attribute table) - broader selection - several map units fall within
> the same type - particular types displayed with different colours -
> prefferebly colours set manually.

from the command line (but similar in gis.m), do it in multiple passes:
 (spearfish dataset example)

d.vect soils type=area where="label ~ 'Va'" fcol=red
d.vect soils type=area where="label ~ 'Ca'" fcol=blue
d.vect soils type=area where="label ~ 'Ma'" fcol=green

d.vect archsites where="cat > 15" col=yellow

Instead of SQL database query with "where=", you can use cats=.

d.vect archsites cat=15-999 col=green

if you want to define a color to be used every time to fill a polygon,
create a new attribute column (usually called "GRASSRGB") with
RRR:GGG:BBB values (0-255), then "d.vect -a rgb_column=GRASSRGB".

and as Maciek mentioned, d.vect.thematic will do this automatically.


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