# addLR: Additive logratio coordinates In robCompositions: Compositional Data Analysis

## Description

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

## Usage

 `1` ```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.

Matthias Templ

## References

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

## See Also

`addLRinv`, `pivotCoord`

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15``` ```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 Jan. 13, 2021, 10:07 p.m.