overlay(SpatialPolygonsDataFrame, SpatialPointsDataFrame)
On Fri, 14 Dec 2007, Ingo Holz wrote:
Hi, I have a SpatialPolygonsDataFrame (SPolyDF) and a SpatialPointsDataFrame(SPoiDF). The SPolyDF is a (very) large set of polygons (some 30.000) and the SPoiDF is actually a grid of some 60.000 points. I would like to use overlay(SPolyDF, SPoiDF) to get the information of the Polygon in a grid, because most of the other information I use is stored / provided in grids. I have two problems:
This is very similar to the thread beginning here: https://stat.ethz.ch/pipermail/r-sig-geo/2007-December/002929.html started yesterday. The issue is the number of polygons, because each polygon is passed the full set of points. The short cut suggested in that thread was to find out which polygon bounding boxes the points fell inside, and then check that much smaller set. This is not in the current code in sp, but contributions are welcome. Roger
1) my PC doesn't have enough memory to do this in "one step".
2) Therefore I used a loop like
result <- numeric(60000)
for (i in 1:60000) {
res <- overlay(SPolyDF[,"name"], SPoiDF[i,]
result[i] <- as.numeric(res)
}
This needs a lot of time.
Is there an easier and/or faster way to get this information with R?
Thanks, Ingo
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Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no