[R-sig-Geo] Fwd: Variogram in spatial package

[Hywel Jones]

A resubmission, as no one has replied and I still have
the problem.
--- Hywel Jones <hywelm.jones at talk21.com> wrote:

> Date: Wed, 17 Jan 2007 09:58:10 +0000 (GMT)
> From: Hywel Jones <hywelm.jones at talk21.com>
> Subject: Variogram in spatial package
> To: r-sig-geo at stat.math.ethz.ch
> 
> The help page for variogram in the spatial package
> leaves my slightly uncertain about a few things. I'd
> be grateful for confirmation of my understanding.
> 
> If I fit a trend surface using surf.ls, and then set
> the krig parameter to use that object in the
> variogram
> function, I'm assuming that the variogram produced
> is
> calculated for the residuals contained in the trend
> surface object. Is that right?
> 
> I'm afraid I don't have the references to check the
> following either. Using notation of Cressie, am I
> right in thinking that the y co-ordinate of the
> variogram corresponds to gamma (or 2x gamma)? And x:
> is that h? 
> 
> And then, how does h correspond to my original data?
> i.e. do I interpret it as distance calculated with
> the
> original x and y submitted to surf.ls, or as
> distance
> calculated with the rescaled x and y used within
> surf.ls (I understand that the internals rescale x
> and
> y to -1:1).
> 
> I'd actually like to check for isotropy before using
> this variogram function. Any suggestions as to
> functions I might use?
> 
> Thanks in advance.
> 
> Hywel
> 
> 
> 		
>
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