[R] Quadratcount problem in spatstat
schutte at icr.gess.ethz.ch
Tue Dec 8 21:38:23 CET 2009
I know there are older threads discussing the quadratcount function in
spatstat. Unfortunately, I could not find a solution to my problem there.
I'm analyzing a point pattern in an irregular polygonal window. Both the
window (an entire country) and the points are projected using WGS84.
When I do quadratcount with only one quadrat for the entire country it
holds all my 154 points:
test <- quadratcount(ppp_cameroon, nx=1, ny=1)
But when I split the country up into several quadrats (which is the only
thing that makes sense for the statistics), the function returns results
that are plainly wrong. The counts always add up to 154, but when
overlaid with the actual points it looks like some points are not at all
counted (0 count quadrats where points are) and some count values are
much higher than they should be (empty quadrats with 20 points).
The problem does not occur with the humberside example data. I can also
reproduce everything in example(quadratcount) correctly with humberside,
but not with my own data set.
Quadrat.test and quadrat.test.ppp lead to the same problem.
I'm out of ideas, so thank you very much for any suggestions!
I'm running R 2.10.0 under Ubuntu Linux 9.10 with spatstat 1.17-2
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