Hotelling (version 1.0-8)

alr: Additive log ratio transformation

Description

Aitchison's additive log ratio tranformation for compositional data

Usage

alr(form, data, group = NULL)

Arguments

form

a formula which specifies the denominator variable as the response

data

a data frame in which the data is stored

group

if not NULL then a character string specifying the name of the grouping variable

Value

a data frame with the ALR transformation applied to data. Each row in the data frame is standardized with respect to a specific variable by dividing by that variable. The logarithms of the resulting ratios are returned. If a grouping variable is specified, then this is preserved.

Details

This function will give a warning if zeros are present because the transformed data will have -Infs.

References

Aitchison, J. (1986). ``The Statistical Analysis of Compositional Data'', Chapman and Hall, reprinted in 2003 with additional material by The Blackburn Press

See Also

clr

Examples

# NOT RUN {
data(bottle.df)

## transform with respect to manganese
alr(Mn~., bottle.df, "Number")

## transform the data with respect to barium, but removing the
## grouping in column 1
alr(Ba~., bottle.df[,-1])
# }