[R-sig-Geo] GSTAT and anisotropy

[Tom Gottfried]

This example

 > library(gstat)
 > data(meuse)
 > coordinates(meuse) <- 1:2
 > sum(variogram(zinc~1, meuse)$np)
[1] 6883
 > sum(variogram(zinc~1, meuse, alpha=45)$np)
[1] 6883
 > sum(variogram(zinc~1, meuse, alpha=45, tol.hor=10)$np)
[1] 1450

shows the effect of the default value of the argument tol.hor 
(documented in the "Usage"-section of ?variogram). Specifying a single 
value for alpha thus gives an isotropic variogram with the default for 
tol.hor.

Am 29.05.2012 06:39, schrieb Michael Hewson:
>
> xv.aeVin <- variogram(g, alpha=c(0, 45, 90, 135))
>
> then I can see the anisotropy for the larger varying variable variogram
> – but the now superimposed graphs contain also the small varying
> variable variogram – and the cross-variogram – these lines are not
> distinguishable from the x-axis in the four plots (thus unreadable for
> analysis).

I assume you plotted xv.aeVin with plot.gstatVariogram. From the 
following example I would conclude you have to provide your own panel 
function or use something else than simply the plot method, as both 
values given to scales yield the same result. But it might well be that 
I missed something here. There are many screws you can screw in the 
world of lattice.

g <- gstat(NULL, "z", zinc~1, meuse)
g <- gstat(g, "l", lead~1, meuse)
plot(variogram(g, alpha=c(45,90,135,0)), scales=list(relation="same"))
plot(variogram(g, alpha=c(45,90,135,0)), scales=list(relation="free"))

HTH,
Tom

> I’m looking for a single plot set (2 variograms and a cross variogram
> for a given direction) – can I achieve that with some code amendments to
> my second set of code above?
>
> Alternatively – can I extent the y axis (semi-variance) in the third set
> of code above?
>
> If it helps I can add the plots …
>
> My thanks,
>
> */________________________________________________________/*
>
> */Michael Hewson /*/PhD candidate/
>
> Climate Research Group <http://www.gpem.uq.edu.au/crg> | Centre for
> Spatial Environmental Research <http://www.gpem.uq.edu.au/cser>
>
> The University of Queensland | Brisbane Q 4072 | Australia
>
> m.hewson at uq.edu.au | */+61 (0)408 379 373/*
>
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