[R-sig-Geo] Moving variance calculation from an irregular grid
Roger.Bivand at nhh.no
Mon Dec 15 16:10:08 CET 2008
On Mon, 15 Dec 2008, Rawlins, Barry G wrote:
> I would like to calculate a moving window variance across a large,
> irregular spatial dataset (1.1 million points) - I have looked for
> various functions but have not been able to find one that will do this.
How irregular? Is the moving window adaptive (k nearest neighbours) or
fixed in distance for a given bandwidth - hence widely varying counts of
points within the window? Do you need the moving window variances for the
same support (points) as the data, or for different points (maybe a grid)?
Could the task be divided up into (overlapping) tiles if memory is a major
constraint? If k nearest neighbours, ANN (approximate nearest neighbours)
has been ported several times to R, but not generalised - I can make one
off-CRAN version available if need be. This thread may be relevant:
> Any suggestions much appreciated.
> Barry R
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
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