[R-sig-Geo] classInterval(style="fisher") vs. ArcView GIS natural breaks

[White.Denis at epamail.epa.gov]

Just found out a little about this in ArcGIS (ArcMap), version 9.1.
Yes, apparently with large datasets, the "natural breaks" classification
(and maybe others like quantile) does sample.  However, it is possible
to change the sample size by clicking the "Sampling" button in the
Classification window.  With 40,000 cases it was really slow, however.

For R users, Roger Bivand's response is more relevant.

r-sig-geo-bounces at stat.math.ethz.ch wrote on 2007-03-16 04:08:42:

> Hi!
>
> 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 ?
>
> Greetings from Strasbourg, France.
>
> Hervé Polesi
>
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