The more I think about it, is this a job for R? I know I need to start using R at some point, just haven't begun yet.
Aren On Wed, May 4, 2011 at 1:42 PM, Aren Cambre <a...@arencambre.com> wrote: > Suppose you have a geometry type with a multipoint. How would you calculate > the variance of the points in that multipoint? > > I looked through the PostGIS 1.5 function reference and am not coming up > with any easy way. > > A hard way seems to be using st_centroid(multipoint) to find the > multipoint's center. From there, I can calculate the distance of each point > from its center, and use that towards calculating the variance (each > distance is squared, all squared distances are added together, then divide > by number of points). > > I guess my ultimate need is to measure relative dispersion of multipoints. > The multipoints that have the most dispersion are suspect, but I need a way > of identifying which ones are like this. > > Aren >
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