I haven't tested it, but the fastest way could be to rasterize your polygon layer (using the resolution of the input raster or higher resolution - make sure to assign an unique id to each grid cell before) and then use r.stats
r.stats -a -p input=rasterized_polygon,raster Rgds, Paulo On Wed, Feb 11, 2015 at 12:15 PM, Margherita Di Leo <[email protected]> wrote: > Hi, > > I have to calculate the percentage of given class of a raster within the > polygons given in a vector (a regular grid). Since I'm dealing with large > files and operations repeated in a chain, i should be focusing on what is > the optimal (fastest) option to do that. I could vectorize the raster and > use v.overlay and v.to.db, or using v.rast.stats i can count out the number > of cells (should i use number for that or sum?) and then divide per area > of the grid. Any better idea? > > Thank you in advance > > -- > Best regards, > > Dr. Margherita DI LEO > Scientific / technical project officer > > European Commission - DG JRC > Institute for Environment and Sustainability (IES) > Via Fermi, 2749 > I-21027 Ispra (VA) - Italy - TP 261 > > Tel. +39 0332 78 3600 > [email protected] > > Disclaimer: The views expressed are purely those of the writer and may not > in any circumstance be regarded as stating an official position of the > European Commission. > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user >
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