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overlay of spatial polygons with GDALReadOnlyDataset
2 messages · Jorge Fernando Saraiva de Menezes, Robert J. Hijmans
Jorge,
You can probably use the raster package. It is not clear what you want
to accomplish with the overlay, but it could be something like this:
Let p be a SpatialPolygons* object
library(raster)
r = raster('filename')
rp = polygonsToRaster(p, r)
z = zonal(rp, r)
or
library(raster)
r = raster(filename)
pv = polygonValues(r, p)
Best, Robert
On Tue, Mar 23, 2010 at 2:04 PM, Jorge Fernando Saraiva de Menezes
<jorgefernandosaraiva at gmail.com> wrote:
Dear all, I'm sorry if this is a too basic question, but I'm trying to make a overlay() of spatial polygon with a srtm ASCII altitude map. I tried to read this map using readasciigrid, but it is to big for the computer's memory. The only way that I find to read this map ?is use GDAL.open, but doesn't seems to have a method to do overlay with GDALReadOnlyDataset. There is some way to use overlay or something like it,with this kind of data, or another way to make overlay() with big grids? Thanks, Jorge ? ? ? ?[[alternative HTML version deleted]]
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