[postgis-users] quantiles, quartiles, or jenks natural breaks

[Paul Ramsey]

I did some in PHP, but the algorithms are relatively braindead, the  
quantile stuff in particular.  Jenks I did some research on but never  
really found a definitive description of the process.  Some of the  
descriptions ended up sounding like a k-means clustering idea, which  
is not cheap!

P.

On 14-Feb-06, at 9:13 AM, David Bitner wrote:

> I'm looking at creating some classification methods for PostGIS data
> for display in MapServer.  I'd like to classify my data using either 5
> quantiles or 5 class Jenks Natural Breaks.  Has anyone out there done
> similar classifications?  I think I could get at the quantiles through
> PL/R (which would entail learning some R), but have no idea where I
> would even start with the Natural Breaks.  Ideally, I'd love to
> perform both of these in PL/PGSQL to keep the number of different PL's
> I use in check.
>
> Has anyone implemented any of these classifications in PostgreSQL?
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