Hello,
In the past I've managed to extract weights using the raster package on
SpatialPolygons. Now when try to extract the weights I get an empty list on
my platform...
I'm simply trying to reproduce this example by Robert J. Hijmans:
/ library(raster)
r <- raster(ncol=36, nrow=18)
r[] <- 1:ncell(r)
cds1 <- rbind(c(-180,-20), c(-160,5), c(-60, 0), c(-160,-60),
c(-180,-20))
cds2 <- rbind(c(80,0), c(100,60), c(120,0), c(120,-55), c(80,0))
polys <- SpatialPolygons(list(Polygons(list(Polygon(cds1)), 1),
Polygons(list(Polygon(cds2)), 2)))
# visualize
plot(r)
plot(polys, add=T)
# extract the cellnumbers and weights
v <- extract(r, polys, weights=TRUE, cellnumbers=TRUE)
v/
This is what I get for v:
/[[1]]
NULL
[[2]]
NULL/
I'm using the latest raster version (1.9-82 (5-April-2012)) and R 2.15.0 I
downgraded to 2.14.2 on a MacOS and still doesn't work (on two different
computers). I went to another machine running on Windows and raster package
v. 1.8-12 (11-April-2011) on R 2.11.1 and it DID work.
So I guess it's about the version of the package? I don't understand what is
going on. Any suggestion would be appreciated!
Thanks.
Ariel
-----
Ariel Ortiz-Bobea
PhD Candidate in Agricultural & Resource Economics
University of Maryland - College Park
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