Hi Thomas, The automatic fitting procedure checks a range of possible variogram models, including Spherical, Exponential, Gaussian and Matern models. Each of these models could lead to a singular model fit. The fitting function in gstat (fit.variogram) says the following on singular model fits:
"""On singular model fits: If your variogram turns out to be a flat, horizontal or sloping line, then fitting a three parameter model such as the exponential or spherical with nugget is a bit heavy: there's an infinite number of possible combinations of sill and range (both very large) to fit to a sloping line. In this case, the returned, singular model may still be useful: just try and plot it. Gstat converges when the parameter values stabilize, and this may not be the case. Another case of singular model fits happens when a model that reaches the sill (such as the spherical) is fit with a nugget, and the range parameter starts, or converges to a value smaller than the distance of the second sample variogram estimate. In this case, again, an infinite number of possibilities occur essentially for fitting a line through a single (first sample variogram) point. In both cases, fixing one or more of the variogram model parameters may help you out. """' regards, Paul Thomas Adams schreef: > Paul, > > This is outstanding; thank you very much! BTW, I noticed that when I > run your example that I get: > > Warning: singular model in variogram fit > > …actually, 2 such warnings with the OK example, and 1 with the UK > example. Are you seeing these too? Otherwise, the results look fine… > > Thanks again for your contribution! > > Regards, > Tom > > > Paul Hiemstra wrote: >> Dear r-sig-geo, >> >> In the course of my PhD I have written a R package that performs >> automatic interpolation (kriging) and might be interesting for other >> people. I work on real-time automatic interpolation of radioactivity >> levels. It depends heavily on the gstat pacakge written by Edzer >> (Pebesma, he is my supervisor). If people are interested in this >> package, it can be downloaded from >> http://intamap.geo.uu.nl/~paul/Downloads.html. If you have any >> comments, complaints or suggestions please do not hesitate to e-mail me. >> >> Some sample code: >> library(automap) >> data(meuse) >> coordinates(meuse) = ~x+y >> data(meuse.grid) >> gridded(meuse.grid) = ~x+y >> kr.ok = autoKrige(log(zinc)~1, meuse, meuse.grid) >> plot(kr.ok) >> kr.uk = autoKrige(log(zinc)~sqrt(dist), meuse, meuse.grid) >> plot(kr.uk) >> >> cheers, >> Paul >> >> > > -- Drs. Paul Hiemstra Department of Physical Geography Faculty of Geosciences University of Utrecht Heidelberglaan 2 P.O. Box 80.115 3508 TC Utrecht Phone: +31302535773 Fax: +31302531145 http://intamap.geo.uu.nl/~paul _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo