compositions (version 2.0-1)

acomparith: Power transform in the simplex

Description

The Aitchison Simplex with its two operations perturbation as + and power transform as * is a vector space. This vector space is represented by these operations.

Usage

power.acomp(x,s)
## Methods for class "acomp"
## x*y
## x/y

Arguments

x

an acomp composition or dataset of compositions (or a number or a numeric vector)

y

a numeric vector of size 1 or nrow(x)

s

a numeric vector of size 1 or nrow(x)

Value

An "acomp" vector or matrix.

Details

The power transform is the basic multiplication operation of the Aitchison simplex seen as a vector space. It is defined as: $$(x*y)_i:= clo( (x_i^{y_i})_i )_i $$ The division operation is just the multiplication with \(1/y\).

References

Aitchison, J. (1986) The Statistical Analysis of Compositional Data Monographs on Statistics and Applied Probability. Chapman & Hall Ltd., London (UK). 416p.

Aitchison, J, C. Barcel'o-Vidal, J.J. Egozcue, V. Pawlowsky-Glahn (2002) A consise guide to the algebraic geometric structure of the simplex, the sample space for compositional data analysis, Terra Nostra, Schriften der Alfred Wegener-Stiftung, 03/2003

Pawlowsky-Glahn, V. and J.J. Egozcue (2001) Geometric approach to statistical analysis on the simplex. SERRA 15(5), 384-398

http://ima.udg.es/Activitats/CoDaWork03/

http://ima.udg.es/Activitats/CoDaWork05/

See Also

ilr,clr, alr,

Examples

# NOT RUN {
acomp(1:5)* -1 + acomp(1:5)
data(SimulatedAmounts)
cdata <- acomp(sa.lognormals)
plot( tmp <- (cdata-mean(cdata))/msd(cdata) )
class(tmp)
mean(tmp)
msd(tmp)
var(tmp)
# }