Hi
My 2 cents here.
I agree with Edzer that from statistical point of view there is not much
point in compare this.
However the software implementation and checking can benefit from it.
Let me try to remember a few possible relevant points for the diferences:
1. the values in the x-axis : some will average distance values while
others will take the mid point of the classes intervals (as done, for
instence in histograms)
2. How to deal with interval borders (<= ou <, >= or >= )
3. How to deal with coincident locations
4. How the maximim distance for the variogram is defined
5. How to deal with NA's in some distance classes and minimum number of
pairs
The packages will have different default options (maybe not aways clearly
documented).
A commom exemple run using all packages would be welcome, and this should
include not only geoR and gstat but also the opthers.
We only have to bear in mind that the choice of empirical variograms will
aways be subjective, according to the options defined by the user.
Best
P.J.
On Wed, 7 Jun 2006, Edzer J. Pebesma wrote:
Date: Wed, 07 Jun 2006 08:59:00 +0200
From: Edzer J. Pebesma <[EMAIL PROTECTED]>
To: john lewis <[EMAIL PROTECTED]>
Cc: r-sig-geo@stat.math.ethz.ch
Subject: Re: [R-sig-Geo] 1. Re: default value for cutoff in gstat variogram()
john lewis wrote:
Hello all,
I did a comparison of gstat, geoR and SPlus 6.1 about 2 years ago with the coal
ash data and found little difference among them after a bit of time making sure
all input parameters were the same. I don't know if I can find those results
but maybe it is time for me to do it again?
Maybe they're not worrying from a statistical point of view, but from
the point of view of code verification I am interested to see them (with
the data & scripts to generated them). The coalash data are only
available in S-Plus, am I right? (We do have an S+SpatialStats licence,
but never got around to set it up for 7.0)
--
Edzer
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Paulo Justiniano Ribeiro Jr
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