[Thuban-list] visual classifier

Frank Koormann frank.koormann at intevation.de
Fri Dec 5 09:50:42 CET 2003

* Moritz Lennert <mlennert at club.worldonline.be> [031204 19:41]:
> Daniel Calvelo said:
> >
> > I also explored natural breaks. I found very scarce literature on the
> > subject.
> >>From what I gathered, natural breaks are based on a kernel approximation
> >> to
> > the data distribution. From previous experience, programming these things
> > needs tuning and lots of special casing. If you have ideas on the subject,
> > they are most welcome.
> >
> We have a fortran program here which was written ages ago and which uses a
> geometrical approach, exploring the slope between data points. If you are
> interested I can send it to you (I will have to check with the authors,
> but I would be very surprised if they weren't willing to release the code
> freely).

Just for completeness or if some problems arise from using the fortran
code: The original paper on natural breaks ("Jenks
optimization") is "Error on Choroplethic Maps: Definitions,
Measurement, Reduction", G. F. Jenks & F. C. Caspall, Annals of the
Association of American Geographers 61 (2), pp. 217-244 (1971)

Should be available via JSTOR (http://www.jstor.org/journals/00045608.html)
if somebody has an account there.

Best regards,


Frank Koormann                             <frank.koormann at intevation.de>
 Professional Service around Free Software       (http://intevation.net/)
 FreeGIS Project                                 (http://freegis.org/)

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