R: Internal function: computes variance of compositional data...

gsi.varwithlosts {compositions} | R Documentation

## Internal function: computes variance of compositional data set with missing/zero values

### Description

Computes an unbiased estimate of the variance of a compositional data set with some missing and zero values.

### Usage

    gsi.varwithlosts(x,giveCenter=FALSE)

### Arguments

`x` | data set of the classes in `compositions`
`giveCenter` | a logical. If TRUE the function reports the mean as an attribute "center" to the result.

### Value

A variance matrix using all the observed information, where some of its components have been downweighted to account for the missing values. ATTENTION: function quite slow. It will be called directly by `var.acomp` and similar generic functions only if `na.action` is set to `na.pass`.

### Note

Do not use gsi.* functions directly since they are internal functions of the package.

### Author(s)

R. Tolosana-Delgado, K.Gerald v.d. Boogaart http://www.stat.boogaart.de

### References

van den Boogaart, K. G., R. Tolosana-Delgado, and M. Bren (2006) Concepts for handling of zeros and missing values in compositional data, In: 2006 Annual Conference of the International Association for Mathematical Geology (IAMG), Universit\'e de Li\'ege, Belgium.

Bren, M., R. Tolosana-Delgado, and K.G. van den Boogaart (2008) News from compositions, the R package. In: Daunis-i-Estadella, J. and Mart\'in-Fern\'a ndez, J.A. (Eds.) Proceedings of the 3rd International Workshop on Compositional Data Analysis, Universitat de Girona, Spain. http://ima.udg.es/Activitats/CoDaWork03

### Examples

    # generates a 3-part compositional data set with missings
    A <- matrix(c(0.5,0.3,0.1, 0.3,0.2,0, 0.1, 0, 0.75),nrow=3)
    Mvar <- 2*ilrvar2clr(A)
    Mcenter <- acomp(c(1,5,2,3))
    x <- rnorm.acomp(100,Mcenter,Mvar)
    colnames(x)<-c("A","B","C","D")
    # eliminate 20 values completely at random
     slost <- sample(1:length(x), size=30)
     x[slost] <- 0
    # compute the variance with losts
    #print(vr <- gsi.varwithlosts(cdt(x)))
    # compare with Mvar

[Package compositions version 2.0-0 Index]