alr {geostats}

additive logratio transformation

Description

Maps compositional data from an n-dimensional simplex to an (n-1)-dimensional Euclidean space with Aitchison's additive logratio transformation.

Usage

alr(dat, inverse = FALSE)

Arguments

dat

an n column data frame or matrix

inverse

if TRUE, applies the inverse alr tranformation

Value

If inverse=FALSE, returns an (n-1) \times m matrix of logratios; otherwise returns an (n+1) \times m matrix of compositional data whose columns add up to 1.

Examples

xyz <- rbind(c(0.03,99.88,0.09),
             c(70.54,25.95,3.51),
             c(72.14,26.54,1.32))
colnames(xyz) <- c('a','b','c')
rownames(xyz) <- 1:3
uv <- alr(xyz)
XYZ <- alr(uv,inverse=TRUE)
xyz/XYZ