alr {chemometrics}

additive logratio transformation

Description

A data transformation according to the additive logratio transformation is done.

Usage

alr(X, divisorvar)

Arguments

X

numeric data frame or matrix

divisorvar

number of the column of X for the variable to divide with

Details

The alr transformation is one possibility to transform compositional data to a real space. Afterwards, the transformed data can be analyzed in the usual way.

Value

Returns the transformed data matrix with one variable (divisor variable) less.

Author(s)

Peter Filzmoser <[e-mail]>

References

K. Varmuza and P. Filzmoser: Introduction to Multivariate Statistical Analysis in Chemometrics. CRC Press, Boca Raton, FL, 2009.

See Also

clr,ilr

Examples

data(glass)
glass_alr <- alr(glass,1)