compositions (version 2.0-8)

compOKriging: Compositional Ordinary Kriging

Description

Geostatistical prediction for compositional data with missing values.

Usage

compOKriging(comp,X,Xnew,vg,err=FALSE)

Value

A list of class "logratioVariogram"

X

The new locations as given by Xnew

Z

The predicted values as acomp compositions.

err

A bug has been found here. This output is currently disabled (An ncol(Z)xDxD array with the clr kriging errors.)

Arguments

comp

an acomp compositional dataset

X

A dataset of locations

Xnew

The locations, where a geostatistical prediction should be computed.

vg

A compositional variogram function.

err

boolean: If true kriging errors are computed additionally. A bug was found here; the argument is currently disabled.

Author

K.Gerald v.d. Boogaart http://www.stat.boogaart.de

Details

The function performes multivariate ordinary kriging of compositions based on transformes addapted to the missings in every case. The variogram is assumed to be a clr variogram.

References

Pawlowsky-Glahn, Vera and Olea, Ricardo A. (2004) Geostatistical Analysis of Compositional Data, Oxford University Press, Studies in Mathematical Geology

Tolosana (2008) ...

Tolosana, van den Boogaart, Pawlowsky-Glahn (2009) Estimating and modeling variograms of compositional data with occasional missing variables in R, StatGis09

See Also

vgram2lrvgram, CompLinModCoReg, vgmFit

Examples

if (FALSE) {
# Load data
data(juraset)
X <- with(juraset,cbind(X,Y))
comp <- acomp(juraset,c("Cd","Cu","Pb","Co","Cr"))
lrv <- logratioVariogram(comp,X,maxdist=1,nbins=10)
plot(lrv)

# Fit a variogram model
vgModel <- CompLinModCoReg(~nugget()+sph(0.5)+R1*exp(0.7),comp)
fit <- vgmFit2lrv(lrv,vgModel)
fit
plot(lrv,lrvg=vgram2lrvgram(fit$vg))

# Define A grid
x <- (0:10/10)*6
y <- (0:10/10)*6
Xnew <- cbind(rep(x,length(y)),rep(y,each=length(x)))

# Kriging
erg <- compOKriging(comp,X,Xnew,fit$vg,err=FALSE)
par(mar=c(0,0,1,0))
pairwisePlot(erg$Z,panel=function(a,b,xlab,ylab) {image(x,y,
                     structure(log(a/b),dim=c(length(x),length(y))),
                     main=paste("log(",xlab,"/",ylab,")",sep=""));points(X,pch=".")})


# Check interpolation properties 
ergR <- compOKriging(comp,X,X,fit$vg,err=FALSE)
pairwisePlot(ilr(comp),ilr(ergR$Z))
ergR <- compOKriging(comp,X,X+1E-7,fit$vg,err=FALSE)
pairwisePlot(ilr(comp),ilr(ergR$Z))
ergR <- compOKriging(comp,X,X[rev(1:31),],fit$vg,err=FALSE)
pairwisePlot(ilr(comp)[rev(1:31),],ilr(ergR$Z))
}