It's to help me double check my interpretation of a large dataset. I have a collection of millions of traffic tickets. Each ticket has route name, milepost, and lat/long. I want to see how well the tickets of a particular route/milepost are to each other.
E.g., all tickets written for US 71, milepost 204--if they have a very large dispersion, then either I have an error in my analysis or the data is not good. Aren On Sat, May 28, 2011 at 2:32 AM, Ben Madin <li...@remoteinformation.com.au>wrote: > I'm not quite clear to me what you are trying to demonstrate - do you want > to know the density of the points... relative to their total size (area / > number?), or relative to some defined area? > > cheers > > Ben > > > On 28/05/2011, at 6:19 AM, Aren Cambre wrote: > > Did anyone have thoughts on this? :-) > > Aren > > On Wed, May 4, 2011 at 2:12 PM, Aren Cambre <a...@arencambre.com> wrote: > >> 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 >>> >> >> > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > >
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