[R-sig-Geo] Subsetting a spatial grid

[Rob Robinson]

Help - please! :-)
 I have what I thought was a really simple problem. I have a raster image of
satellite data from which I would like to extract an arbitrary (but simple
rectangular) portion for subsequent analysis (which I'll need to do for many
images). I have the data as a (projected) SpatialGridDataFrame and have
tried two approaches: create a SpatialPolygon and overlay it (but I don't
think overlay does what I would like it to do), or access the coords slot of
the data set and pick those within the range. I haven't been able to get
either to work - presumably because my R is not good enough! It seems a
fairly common task, but I haven't yet stumbled across an FAQ or page in
ASDAR which seems to help. Any pointers anyone?
Many thanks for any help
Cheers
rob

*** Want to know about Britain's birds? Try  www.bto.org/birdfacts ***

Dr Rob Robinson, Senior Population Biologist
British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU
Ph: +44 (0)1842 750050        E: rob.robinson at bto.org
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