optimize idw power

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Dominik,

The brute force approach shown in the link from Tom has in the mean time 
been implemented in the intamap package. See the example for the 
function "estimateParameters".

Cheers,
Jon
Dominik,

Look here:
http://r-sig-geo.2731867.n2.nabble.com/GSTAT-Optimize-power-value-for-IDW-td2765918.html

Tom

On Mon, Aug 12, 2013 at 5:17 PM, Dominik Schneider <
Dominik.Schneider at colorado.edu> wrote:

Hi,
I'd like to optimize the IDW power, similar to what ArcGIS does. I found
this old thread
http://www.mail-archive.com/r-sig-geo at stat.math.ethz.ch/msg04011.html but
was hoping someone could help adapt the solution. I am using

idw(residuals(mdl.stepaic[[j]])~1,locations=swe.nozeros[swe.nozeros$mth==mth
& swe.nozeros$yr==yr,],newdata=swe.grid)

where mdl.stepaic[[j]] is a list of 39 regression equations. swe.nozeros is
a spatialpointsdataframe of observations. swe.grid is a grid where I want
new values predicted. I currently run this idw command through a loop of j
with no problems but I'd like to optimize both within each equation
represented by j and for the whole data set (so across the 39 timesteps).

Below is what I'm starting with but I don't really understand how to get it
working. I appreciate your help.

f= function(idp,formula,locations,newdata,...) {

sum(idw(formula,locations,newdata),set=list(debug=0,idp=idp),...)$residuals**2
}

optimize(f,interval=seq(1.4,1.7,by=0.1),formula=residuals(mdl.stepaic[[j]])~1,locations=swe.nozeros[swe.nozeros$mth==mth
& swe.nozeros$yr==yr,],newdata=swe.grid)

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Jon Olav Sk?ien
Joint Research Centre - European Commission
Institute for Environment and Sustainability (IES)
Land Resource Management Unit

Via Fermi 2749, TP 440,  I-21027 Ispra (VA), ITALY

jon.skoien at jrc.ec.europa.eu
Tel:  +39 0332 789206

Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission.
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