It looks quite OK; I suspect however that instead of using mean(s.v$gamma) for SSTot, for this mean the same weighting scheme should have been used. -- Edzer
On 09/02/2010 02:59 PM, k...@grf.rs wrote: > > Hi list, > > I'm not sure in my calculation of R2 coefficient of determination for > variogram. Could someone check it, or give the better way. > > Here is an example: > > library(sp) > library(gstat) > > data(meuse) > coordinates(meuse) <- ~x+y > s.v<- variogram(log1p(zinc)~sqrt(dist), meuse) > vr.fit <- fit.variogram(variogram(log1p(zinc)~sqrt(dist), meuse), vgm(0, > "Exp", 300, 1)) > > ## SSErr is it summ of weighted squares of residuals ? > (SSErr<-attr(vr.fit,"SSErr")) > > ## SStot total sum of weighted squares > > weig<-s.v$np/s.v$dist^2 #fit.method fitting method, used by gstat. The > default method uses weights $N_h/h^2$ with $N_h$ the number of point pairs > and $h$ the distance. > > > (SStot<- sum(weig*(s.v$gamma-mean(s.v$gamma))^2) ) > (R2<-1-SSErr/SStot ) # R2 coefficient of determination > > Best regards, > Kili > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo -- Edzer Pebesma Institute for Geoinformatics (ifgi), University of Münster Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de http://www.52north.org/geostatistics e.pebe...@wwu.de _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
