clr {Hotelling}

Centered log ratio transformation

Description

Aitchison's centered log ratio tranformation for compositional data

Usage

clr(data, group = NULL)

Arguments

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

Details

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

Value

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

Author(s)

James M. Curran

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

alr

Examples

data(bottle.df)

## transform preserving grouping
clr(bottle.df, "Number")

## transform the data but remove the
## grouping in column 1
clr(bottle.df[,-1])