DESCRIPTION

d.vect.thematic creates thematic maps from vectors of all types and numeric attributes (stored in the data table connected to a vector map). Thematic maps can be displayed by either a graduated color scheme (for all vector types), as graduated icon sizes (for point and centroid types), or graduated line widths (for lines and boundaries with associated attributes). The user selects the vector map to be mapped and attribute column from which to derive mapping intervals, and (optionally) the layer for attribute data.

In thematic maps, the color or point size changes for each range of attribute values. Value ranges for thematic mapping can be set at regular intervals, standard deviation units on either side of the mean, quartiles, or delimited by user-defined breakpoints. User-defined breakpoints also can be entered, or piped into d.vect.thematic from standard input or other external source.

There are options to define the color scheme (graduated colors) and range of point sizes (graduated points) for thematic maps. A simple text legend is printed. Optionally, a graphic legend can be drawn in the selected display monitor. Thematic colors can be uploaded to a GRASSRGB column for later display, and thematic map display commands can be saved to a group file (*.dm) that can be opened, edited, and displayed in the GIS Manager.

When the psmap option is set to 'name', two psmap instruction files are created (in the current directory if no path is given), one for the map ('name.psmap') and one for the legend ('name_legend.psmap'). The map file also contains 'label' commands which allow to create a legend directly in the map by adding a 'vlegend' command. See the ps.map man page for more details.

NOTES

The algorithm currently uses the v.univar.sh to calculate basic descriptive statistics needed for thematic mapping (minimum, maximum, mean, standard deviation, and quartiles).

EXAMPLES

Earthquake points with color gradient: 
d.vect.thematic -l recent_earthquakes column=magnitude type=point

Earthquake points with different sizes: 

d.vect.thematic -l recent_earthquakes column=magnitude type=point \
                themetype=graduated_points maxsize=15

Spearfish: differences between 'elevation.10m' and 'elevation.dem': 

# random sampling of elevation points:
g.region rast=elevation.10m -p
v.random random n=200
v.db.addtable random col="el10 double precision"
# transfer elevations to attribute table of random points map:
v.what.rast random rast=elevation.10m col=el10
v.db.select random

# comparative sampling of second map, incl. differences:
v.sample in=random col=el10 rast=elevation.dem out=elev_sample
v.db.select elev_sample

# thematic map:
d.mon x0
d.vect.thematic -l elev_sample column=diff type=point

North Carolina data set example: 

g.region vect=nc_state
d.vect.thematic -l precip_30ynormals column=annual type=point

SEE ALSO

d.vect, d.vect.chart, v.univar.sh

AUTHORS

Michael Barton, Arizona State University, Daniel Cavelo Aros, Martin Landa, and Jachym Cepicky.

Last changed: $Date: 2008-08-15 08:16:42 +0200 (Fri, 15 Aug 2008)$