Geostatistical R Package - Board

Hi,

I would like to know how one describes a drift ( e.g., a second order polynomial drift in a 2-D space) through the parameter uc= of the functions vario.calc() and kriging(). I note that the command uc.names() specified in the documentation does not exist in the package.

Thanks,

Francky

Edit moderation: I move this post in the kriging section.

Dear Francky,

here is a short script using a data set of RGeostats to explain how to perform universal kriging.

Load the data:

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data(Exdemo_ext.data)
dat=Exdemo_ext.data #to do shorter


Perform the variography and the modeling:

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vario=vario.calc(dat)
model1=model.auto(vario,struct=c("K-Bessel","Nugget Effect"))


Create the output grid and the neighborhood (unique):

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grid=db.create(nx=c(200,200))
unique=neigh.init(type=0)


Perform ordinary kriging:

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grid=kriging(dat,grid,neigh=unique,model=model1)
plot(grid,pos.legend=1,zlim=c(-4,5))
plot(dat,add=T)

Perform universal kriging with a second order polynomial drift:

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x11()
grid=kriging(dat,grid,neigh=unique,model=model1,uc=c("1","x","y","xy","x2","y2"))
plot(grid,pos.legend=1,zlim=c(-4,5))
plot(dat,add=T)


It seems that there is not a great difference (it is probably due to the
fact that drift is useless in this specific case and the data control the result.
However we can see some differences far from the data points:

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grid=db.add(grid,grid[,6]-grid[,4],loctype="z")
plot(grid,pos.legend=1)
plot(dat,add=T)


I hope it helped you.
I am not really aware about universal kriging

Regards,
Nicolas

Dear Nicolas,

Thank you so much,

Regards,

Francky