Dear Javier,

- you don't have a lot of points
- did you plot the raw variogram? Then you see that there is something odd going on: a high semivariance a short range, then a drop in the variance. That's probabliy why you get the singular fit
- looking at a plot of your dataset, it seems like see will need an anisotrope variogram model.

Best regards,

Thierry

Van: r-sig-geo-bounces@r-project.org [mailto:r-sig-geo-bounces@r-project.org] Namens Javier Leon Patino
Verzonden: donderdag 15 september 2011 9:40
Aan: r-sig-geo@r-project.org
Onderwerp: [R-sig-Geo] singular model fit

Dear list,

I am aware there are many post dealing with singular model variogram fits but I have not been able to fix my problem even after re-scaling the coordinates and variables.

I am using fit.variogram(gstat) on the file 'trans.csv' (attached) and have tried several values for the range, sill and nugget and different models. The following gives me an ok variogram (from visual plot) but still a 'singular model' warning.

library(sp)
library(gstat)
points <- read.csv("trans.csv")
coordinates(points)=~x+y
depth.ivgm <- vgm(model='Gau',range=1000, psill=var(points$ln_depth))
depth.vgm <- fit.variogram(variogram(ln_depth~x+y, points), model=depth.ivgm)

Any ideas on why I am getting a singular fit? Is it the small number of samples used?

Cheers,

Javier


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