transform_alr function

Additive Log-Ratios (ALR)

Computes ALR transformation. methods

transform_alr(object, ...)

## S4 method for signature 'CompositionMatrix'
transform_alr(object, j = ncol(object), weights = FALSE)

## S4 method for signature 'GroupedComposition'
transform_alr(object, j = ncol(object), weights = FALSE)

## S4 method for signature 'CLR'
transform_alr(object, j = ncol(object))

## S4 method for signature 'GroupedCLR'
transform_alr(object, j = ncol(object), weights = FALSE)

Arguments

• object: A CompositionMatrix object.
• ...: Currently not used.
• j: An integer giving the index of the rationing part (denominator).
• weights: A logical scalar: should varying weights (column means) be computed? If FALSE (the default), equally-weighted parts are used. Alternatively, a positive numeric vector of weights can be specified (will be rescaled to sum to $1$). Weights will be used internally by other methods (e.g. variance()).

Returns

An ALR object.

Details

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

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)

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. tools:::Rd_expr_doi("10.1146/annurev-statistics-042720-124436") .

See Also

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

Author(s)

N. Frerebeau