Hello R Users,
I am trying to do a quadrat count defined by covariate properties in
spatstat. I have read my elevation raster into R (from ascii) and converted
to class "im" for use in spatstat.
Now I have point data of class "ppp" which window is the same extent as the
elevation image. I can conveniently plot the image and the points on the
image as follows:

>plot(elevation, axes=T, col=terrain.colors(20))
>plot(points, add=T, cex=0.5)

I have also created a tessellation of the elevation image into 4 categories
as follows:

>elev.cut<-cut(elevation.im, breaks=elev.quantiles, labels=c("Very
low","Low","High","Very High"))
>elev.tess<-tess(image=elev.cut)

I would like to do a quadrat count to know how many points lie in each of
the elevation categories I have created, and as far as I know, this function
should give that:

>elev.quad.count<-quadratcount(points, tess=elev.tess)

But when I do this, I get a warning message saying:

Warning message:
In quadratcount.ppp(points, tess = aspect.tess) :
  Tessellation does not contain all the points of X

I have checked and the extent of the tessellated elevation image is
different from the original elevation image (smaller). Is there anything I
am missing here?
Please any help will be appreciated.



-- 
Neba, Funwi-Gabga

Erasmus Mundus Masters
Geospatial technologies,
Superior School of Experimental Sciences and Technology,
Universitat Jaume I
Castellon, Spain.

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