[R-sig-Geo] singular model fit

[Tom Gottfried]

Hi Javier,

Am 15.09.2011 09:40, schrieb Javier Leon Patino:
> 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))

you use the variance of ln_depth as an estimate for the sill here. Thus, I suspect you want the 
variogram of ln_depth.

> depth.vgm <- fit.variogram(variogram(ln_depth~x+y, points), model=depth.ivgm)

What you calculate here with variogram() is a residual variogram of ln_depth from a first order 
trendsurface over your coordinates. Might that be the cause?

Tom

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