Hi,
Which version of R and sp are you using? I'm asking this because I had a
similar problem as you had with a raster of 50.000+ points and some 7000
polygons (not sure if this is comparable to your dataset). Doing the
overlay took far too long, but after a question about this to the
r-sig-geo list, Roger Bivand extended the code for point.in.polygon to
first make a subset of the polygons based on the bounding boxes of the
polygons (fast operation) and then perform a point in polygon operation.
I'm not really sure from which version of sp this feature is included,
but it should be included in the latest version (Roger?). Maybe an
upgrade would solve your problem, it did mine.
hope this helps,
Paul
Pieter Beck wrote:
Dear all,
I am a new user to the world of spatial applications of R and am wondering
about this trivial question:
What is the easiest way to subset a SpatialGridDataFrame, based on 4 corner
coordinates?
The reason I ask is that I want to do an overlay of a polygon file on a
large raster dataset, to extract summary statistics from it. Both files are
extremely large, however, and just applying overlay causes memory trouble. I
was hoping to loop through the polygons, subset the SpatialGridDataFrame
using the bounding box surrounding a polygon and then create the summary
statistics one polygon at-a-time. To do this, I'd need to subset the
SpatialGridDataFrame based on the bounding box corner coordinates.
Thanks in advance for the help,
Kind Regards,
Pieter Beck
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Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
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