On 05/10/11 07:10, Micha Silver wrote: > > On Tue, 2011-10-04 at 16:55 +0200, Sebastian Schubert wrote: >> Hi, >> >> I have a map with several polygons i, each having a certain value x_i. I >> want to calculate the average value of x in a rectangular grid. Each >> cell j of this grid includes (parts of) several polygons with A_ij being >> the area of the part of polygon i being in grid cell j. With that the >> average value in grid cell j is >> >> x_j = sum_i A_ij x_i / (sum_i A_ij) >> >> I was able to create a grid with Vector > Research Tools > Vector grid. >> Now each cell of this grid should include the average value of all >> polygons inside the cell (as described above). >> >> Any idea how to do that? >> > > You probably want to look at the GRASS module v.rast.stats
Thanks for the hint. This, however, does exactly the opposite. Statistics of raster based values controlled by a vector file. I have the values in the vector polygons and I want to calculate the statistics based on the pixels of a raster map. What I did was basically convert the vector map to a very fine raster file and then use the function r.resamp.stats to calculate the values for the wanted coarse resolution. Cheers Sebastian
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