GWR

Attached you will find the scripts and results from R and a comparation of 
the coefficients from both R and GWR 3.0. Hope you can help me to figure out 
the reason of the big differences.
Two reasons:

1) The GWR adaptive proportion to include is stated to be about 23 
observations of 50, the R one was about 19. 

2) You were using the arguments in gwr() wrongly. When doing adaptive GWR,
you should pass the output of gwr.sel() through the adapt= argument, and
should not include bandwidth=. For your data, with adapt=col.dd and
adapt=(23/50), you get results much more like GWR3 - for 23/50 agreeing
pretty closely.

Hope this helps,

Roger
Thank you very much.

From: Roger Bivand <Roger.Bivand at nhh.no>
Reply-To: Roger.Bivand at nhh.no
To: CARMEN RODRIGUEZ <carm_rodrig at hotmail.com>
CC: r-sig-geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] GWR
Date: Wed, 29 Nov 2006 11:33:56 +0100 (CET)

On Wed, 29 Nov 2006, CARMEN RODRIGUEZ wrote:

I insist on GWR. To run a GWR model I'm using both R and GWR 3.0. 
Comparing
the estimated coefficients for an adaptative bisquare kernel in R with 
the
results for an adaptative kernel in GWR 3.0 (which is supposed to be a
bisquare function too), differences are very big. I check the bandwidths 
and
they are not that different (as I understand, in R the adaptative 
bandwidth
is expressed as a percentage of observations, while in GWR 3.0 the 
bandwidth
is the number of observations itself). But anyway, the estimated
coefficients shouldn't be so different, should they?
Well, without documentation, it is impossible to tell. So please provide
documentation, access to data and scripts of what you are doing that
worries you. We cannot see over your shoulder.

Roger

Thank you.

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--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no

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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no