subsetting
Pieter, the easiest in terms of the least mental exercise might be to form a polygon from the four points and then overlay that with the grid. This will likely be too slow and/or memory intensive. The more efficient way would be to compute the row and column index ranges from the bounding box, and index the SpatialGridDataFrame with that. gridparameters(x) gives you the necessary information for this. -- Edzer
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 [[alternative HTML version deleted]]
_______________________________________________ R-sig-Geo mailing list R-sig-Geo at stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Edzer Pebesma Institute for Geoinformatics (ifgi), University of M?nster Weseler Stra?e 253, 48151 M?nster, Germany. Phone: +49 251 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de/ http://www.springer.com/978-0-387-78170-9 e.pebesma at wwu.de