[R-sig-Geo] creating irregularly-shaped grids for kriging

[Paul Hiemstra]

Hi Craig,

The easiest way is to get a polygon of you study area and than use 
spsample() to create a grid. You could also make a convex hull using the 
chull command and spsample from that. Depending on your configuration of 
points this might be an option. You could try autoKrige from the automap 
pacakge to get an idea of how this last option looks, it uses a convex 
hull to create a new_data object if it is not given.

library(automap)
data(meuse)
coordinates(meuse) = ~x+y

kr = autoKrige(meuse)
plot(kr)

cheers,
Paul

Scanlan, Craig wrote:
> Hi all,
>  
> I need to krige data that is irregularly spaced within irregularly
> shaped areas (agricultural fields).   
>  
> At present, I am creating a regular grid for newdata in
> krige(data,newdata....) by
>  
> x.range <- as.integer(range(a2 at coords[,1]))
> y.range <- as.integer(range(a2 at coords[,2]))
> grd <- expand.grid(x=seq(from=x.range[1], to=x.range[2], by=10),
> y=seq(from=y.range[1], to=y.range[2], by=10) )
>
> I have not been able to find a method to trim the newdata grid to the
> same shape as the original data - is this possible?
>  
> The task I am trying to achieve is the same as creating meuse.grid from
> meuse data.
>  
> Can anyone help?
>  
> Regards,
>  
> Craig.
>  
>
>
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-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 274 3113 Mon-Tue
Phone:  +3130 253 5773 Wed-Fri
http://intamap.geo.uu.nl/~paul