R: Empirical variograms for compositions

logratioVariogram {compositions} | R Documentation

## Empirical variograms for compositions

### Description

Computes the matrix of logratio variograms.

### Usage

    logratioVariogram(comp,
                              loc,
                              maxdist=max(dist(loc))/2,
                              nbins=20,
                              dists=seq(0,maxdist,length.out=nbins+1),
                              bins=cbind(dists[-length(dists)],dists[-1]),
                              azimuth=0,
                              azimuth.tol=180
                              )

### Arguments

`comp` | an acomp compositional dataset
`loc` | a matrix or dataframe providing the observation locations of the compositions. Any number of dimension >= 2 is supported.
`maxdist` | the maximum distance to compute the variogram for.
`nbins` | The number of distance bins to compute the variogram for
`dists` | The distances seperating the bins
`bins` | a matrix with lower and upper limit for the distances of each bin. A pair is counted if min<h<=max. min and max are provided as columns. bins is computed from maxdist,nbins and dists. If it is provided, it is used directly.
`azimuth` | For directional variograms the direction, either as an azimuth angle (i.e. a single real number) for 2D datasets or a unit vector pointing of the same dimension as the locations. The angle is clockwise from North in degree.
`azimuth.tol` | The angular tolerance it should be below 90 if a directional variogram is intended.

### Details

The logratio-variogram is the set of variograms of each of the pairwise logratios. It can be proven that it carries the same information as a usual multivariate variogram. The great advantage is that all the funcitions have a direct interpreation and can be estimated even with (MAR) missings in the dataset.

### Value

A list of class `"logratioVariogram"`.

`vg` | A nbins x D x D array containing the logratio variograms
`h` | A nbins x D x D array containing the mean distance the value is computed on.
`n` | A nbins x D x D array containing the number of nonmissing pairs used for the corresponding value.

### Author(s)

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

### References

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

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

### See Also

`vgram2lrvgram`, `CompLinModCoReg`, `vgmFit`

### Examples

    ## Not run:
    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)

    ## End(Not run)

[Package compositions version 1.40-5 Index]