| addLR {robCompositions} | R Documentation |
The additive log-ratio transformation moves D-part compositional data from the simplex into a (D-1)-dimensional real space.
addLR(x, ivar = ncol(x), base = exp(1))
x |
D-part compositional data |
ivar |
Rationing part |
base |
a positive or complex number:
the base with respect to which logarithms are computed. Defaults to |
The compositional parts are divided by the rationing part before the logarithm is taken.
A list of class “alr” which includes the following content:
x.alr |
the transformed data |
varx |
the rationing variable |
ivar |
the index of the rationing variable, indicating the column number of the rationing variable in the data matrix x |
cnames |
the column names of x |
The additional information such as cnames or ivar is usefull when a back-transformation is applied on the ‘same’ data set.
Matthias Templ
Aitchison, J. (1986) The Statistical Analysis of Compositional Data Monographs on Statistics and Applied Probability. Chapman \& Hall Ltd., London (UK). 416p.
data(arcticLake) x <- arcticLake x.alr <- addLR(x, 2) y <- addLRinv(x.alr) ## This exactly fulfills: addLRinv(addLR(x, 3)) data(expenditures) x <- expenditures y <- addLRinv(addLR(x, 5)) head(x) head(y) ## --> absolute values are preserved as well. ## preserve only the ratios: addLRinv(x.alr, ivar=2, useClassInfo=FALSE)