Message-ID: <4E71B433.60403@tum.de>
Date: 2011-09-15T08:15:47Z
From: Tom Gottfried
Subject: singular model fit
In-Reply-To: <D8457815528063439E5066EE2475CF1C0A4B7EC37C@UQEXMB04.soe.uq.edu.au>
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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