v.colors(1)

NAME
v.colors

DESCRIPTION
v.colors is much like r.colors, but may be used for vector maps. You give it a vector map and numeric data column, together with color rules like you would do for a raster. It creates a new column in the database with R:G:B values suitable for use with 'd.vect -a'.

How it works: it creates a dummy raster map with the same data range as the vector's column then runs r.colors for that temporary map. It then uses r.what.colors for each value found by v.db.select and uploads it a new column in the vector map's attribute database.

It is planned that this script will be replaced with a C display module which renders thematic vector maps directly instead requiring the overhead of saving the colors into the DB.

If the target column name given by the rgb_column option does not exist, it will be created. The default name is "GRASSRGB".

EXAMPLES
Create a random sample point map, query raster map values for those points, and colorize output.
# Spearfish dataset
g.region -d
v.random out=rand5k_elev n=5000
v.db.addtable map=rand5k_elev column='elevation double precision'
v.what.rast vector=rand5k_elev raster=elevation.10m column=elevation
v.colors map=rand5k_elev column=elevation color=bcyr
# display colorized points map
d.mon x0
d.vect -a rand5k_elev

Colorizing the roads map in Spearfish:
g.copy vect=roads,myroads
echo "1 red
2 yellow
3 orange
4 black
5 grey" > colors.txt
v.colors myroads column=cat rules=colors.txt
# display colorized roads map
d.mon x0
d.vect -a myroads

Colorizing a TIN (polygons) generated by v.delaunay:
# new columns for x,y,z of centroids
v.db.addtable map=tin \
   columns="east double precision, north double precision, height double precision, GRASSRGB varchar(11)"
# transfer geometry for colorizing (we need the centroid height)
v.to.db tin option=coor columns="east,north,height"
v.db.select tin
v.colors tin column=height rgb_column=GRASSRGB color=rainbow
# display colorized triangles
d.mon x0
d.vect -a tin

SEE ALSO
d.vect -z
r.colors
r.colors.stddev
r.what.color
v.db.addcol
v.db.select
db.execute

AUTHOR
Hamish Bowman
Dunedin, New Zealand

Last changed: $Date: 2009-02-09 14:06:52 +0100 (Mon, 09 Feb 2009) $

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