[R-sig-Geo] classInterval(style="fisher") vs. ArcView GIS natural breaks
Roger.Bivand at nhh.no
Fri Mar 16 14:52:47 CET 2007
On Fri, 16 Mar 2007, Hervé Polesi wrote:
> Working on a litle datebase (903 lines) I notice a difference between
> the result of classInterval(style="fisher") and the natural breaks
> proposed by ArcView GIS (3.2).
> I read that ArcView works on a sample of data. Is it right ? May it
> cause a significative difference ?
The classInt package is open source, but ArcView/ArcGIS isn't (unless you
consider the new python scripts, but I don't think these include class
intervals). Is it possible to check in the ESRI documentation? I recall
being told that the symbology is built on the fly and probably stored in
the project, and that a sample is used instead of the total. If anyone
has some students who'd like to deconstruct the ESRI approach by testing
on known distributions, that might be fun. We have the Fisher code (as
implemented), so seeing why things might differ ought to be possible.
Of course, there are very many different classifications anyway, even for
moderate n and k.
> Greetings from Strasbourg, France.
> Hervé Polesi
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
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e-mail: Roger.Bivand at nhh.no
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