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

[David Bitner]

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?