[GRASS-user] Raster Maps

[Andrew Lewin]

Hi Everyone,

I would like to create a raster map of temperature values using v.surf.idw and calculate the median temperature value for each state/province in North America.  I currently have a point shapefile of temperature values covering all of North America, a North American area shapefile (both imported using v.in.ogr).  I would like to use v.rast.stats to calculate the median value for each state/province; however, I get an "Error: no categories found in raster map".  I created the temperature value raster using v.surf.idw and there are no categories associated with this file.

Can anyone tell me how I can assign categories to a raster file please?

I am running Grass 6.4 on a Mac OSX Snow Leopard.

Cheers,

Andrew

Andrew Lewin, M.Sc., Adv. Dipl. GIS
President
Spatial-Conserve Inc.
Oceans and Coasts Blog at www.spatialconserve.com
Email: alewin at spatialconserve.com
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