polygons to grid?
Hi Agus, In this function, and in all other functions in 'raster', the values of a new RasterLayer object are written to disk if they cannot be stored in memory (they are saved in a temporary file that is erased the next time you load the package). To force writing to disk, and to a more permanent file, you can provide an argument "filename= " (and "format= " to choose the file format). Robert
On Sat, Nov 21, 2009 at 11:28 AM, Agustin Lobo <Agustin.Lobo at ija.csic.es> wrote:
Perfect, this is what I do: #Equivalent to #v.to.rast input=visit output=visitCODEQP use=attr column=CODI_EQP visitCODEQP <- raster(extent(visit)) res(visitCODEQP) <- 100 visitCODEQP <- polygonsToRaster((spPolys=visit, raster=visitCODEQP,field="CODI_EQP") [1] "Found 39 regions and ?39 polygons" [1] "finished in ?0 minutes, at 0 seconds/row" Just a concern: is the new raster (visitCODEQP in the example) loaded into memory? Potentially, it could be very large. Thanks a lot! Agus Robert J. Hijmans wrote:
Agus, Please see ? raster::polygonsToRaster Let 'p' be a SpatialPolygonsDF. Create an appropriate RasterLayer object, for example use the extent of the polygons and set the resolution. r <- raster(extent(p)) res(r) <- 1 # then: r <- polygonsToRaster(p, r) ? # there are additional arguments to consider # to coerce into a SPGDF spg <- as(r, 'SpatialGridDataFrame') There was a discussion earlier this year, I believe, where there was also an example to do this entirely in sp (using point in polygon overlays) Robert On Sat, Nov 21, 2009 at 5:20 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
Hi? Is it possible to perform a vector to raster conversion in R, from SpatialPolygonsDataFrame to a SpatialGrid (providing the final resolution? In particular, is it possible to do it using package raster? (I know this can be done using gdal or grass etc, but I'm trying to find an "only R" solution) Thanks Agus
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-- Dr. Agustin Lobo Institut de Ciencies de la Terra "Jaume Almera" (CSIC) LLuis Sole Sabaris s/n 08028 Barcelona Spain Tel. 34 934095410 Fax. 34 934110012 email: Agustin.Lobo at ija.csic.es http://www.ija.csic.es/gt/obster