addLR: Additive logratio coordinates

In robCompositions: Compositional Data Analysis

Additive logratio coordinates

Description

The additive logratio coordinates map D-part compositional data from the simplex into a (D-1)-dimensional real space.

Usage

addLR(x, ivar = ncol(x), base = exp(1))

Arguments

x	D-part compositional data
ivar	Rationing part
base	a positive or complex number: the base with respect to which logarithms are computed. Defaults to exp(1).

Details

The compositional parts are divided by the rationing part before the logarithm is taken.

Value

A list of class “alr” which includes the following content:

x.alr	the resulting coordinates
varx	the rationing variable
ivar	the index of the rationing variable, indicating the column number of the rationing variable in the data matrix x
cnames	the column names of x

The additional information such as cnames or ivar is useful when an inverse mapping is applied on the ‘same’ data set.

Author(s)

Matthias Templ

References

Aitchison, J. (1986) The Statistical Analysis of Compositional Data Monographs on Statistics and Applied Probability. Chapman and Hall Ltd., London (UK). 416p.

See Also

addLRinv, pivotCoord

Examples

data(arcticLake)
x <- arcticLake
x.alr <- addLR(x, 2)
y <- addLRinv(x.alr)
## This exactly fulfills:
addLRinv(addLR(x, 3))
data(expenditures)
x <- expenditures
y <- addLRinv(addLR(x, 5))
head(x)
head(y)
## --> absolute values are preserved as well.

## preserve only the ratios:
addLRinv(x.alr, ivar=2, useClassInfo=FALSE)

robCompositions documentation built on Aug. 25, 2023, 5:13 p.m.