Additive Log-Ratios (ALR)

Computes ALR transformation.

Usage

transform_alr(object, ...)

# S4 method for CompositionMatrix
transform_alr(object, j = ncol(object))

Arguments

object

A CompositionMatrix object.

...

Currently not used.

j

An integer giving the index of the rationing part (denominator).

Value

An ALR object.

Details

The ALR transformation is the logratio of a pair of parts with respect to a fixed part.

References

Aitchison, J. (1986). The Statistical Analysis of Compositional Data. London: Chapman and Hall.

Greenacre, M. J. (2019). Compositional Data Analysis in Practice. Boca Raton: CRC Press.

Greenacre, M. J. (2021). Compositional Data Analysis. Annual Review of Statistics and Its Application, 8(1): 271-299. doi:10.1146/annurev-statistics-042720-124436 .

See also

Other log-ratio transformations: transform_clr(), transform_ilr(), transform_inverse(), transform_lr(), transform_plr()

Author

N. Frerebeau

Examples

## Data from Aitchison 1986
data("hongite")

## Coerce to compositional data
coda <- as_composition(hongite)

## Additive log-ratio
alr <- transform_alr(coda)

## Inverse transformation
inv_alr <- transform_inverse(alr)
all.equal(coda, inv_alr)
#> [1] TRUE