Hello all,

I searched the internet very long for an answer, but didn't find one, so I
hope you can help me.

I have to test several study sites for representativeness for the
environment and therefore I have remotely sensed raster data, which
reproduce the NDVI (Normalized Differenced Vegetation Index). The pixel
values vary between -1 and 1. I've also got the coordinates of the study
sites' centers and all the coordinates for all pixels and their values.

For this purpose I decided to calculate variograms for the study sites and
their environment with the variog()-function of the geoR-Package.
Unfortunately, with this function it is only possible to calculate the
semi-variances for each pair of points in the investigated area and not for
pairs of one specific point and any other point (if I understood the R
Documentation correctly). So the calculated semi-variances have nothing to
do with study sites, as they have no spatial connection. Could you please
tell me, if it is possible to calculate these variograms with a given
starting point? I.e. is it possible to calculate the semivariances between
one specific point( the "starting point", which is one study site) and all
other points (the environment of the study sites), which are located in
different distances? Is it possible to do so with variog() or do have to
calculate with other packages like gstat, spatial or nlme?

In the gstat-manual (www.gstat.org/gstat.pdf) I found a so-called local
neighbourhood selection. Is there anything similar available for the geoR
package? If not, how can I implement the commands in the
variogram()-function of the gstat-package? Can I use this local
neighbourhood selection at all or is it a wrong aprroach?

Thank you very much for any answer!
Laura

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