ilt {compositions}R Documentation

Isometric log transform

Description

Compute the isometric log transform of a vector (dataset) of amounts and its inverse.

Usage

          ilt( x )
          ilt.inv( z  )
          

Arguments

x a vector or data matrix of amounts
z the ilt-transform of a vector or data matrix of ilt-transforms of amounts

Details

The ilt-transform maps D amounts (considered in log geometry) isometrically to a D dimensional euclidean vector. The ilt is part of the aplus framework.
The data can then be analysed in this transformation by all classical multivariate analysis tools. The interpretation of the results is easy since the relation to the original variables is preserved.

The isometric log transform is given by

ilt(x)_i := ln x_i

Value

ilt gives the isometric log transform, i.e. simply the log of the argument, ilt.inv gives amounts with the given ilt, i.e. simple the exp of the argument

Author(s)

K.Gerald v.d. Boogaart http://www.stat.boogaart.de

References

See Also

ilr, iit, aplus

Examples

(tmp <- ilt(c(1,2,3)))
ilt.inv(tmp)
ilt.inv(tmp) - c(1,2,3) # 0
data(Hydrochem)
cdata <- Hydrochem[,6:19]
pairs(ilt(cdata)) 

[Package compositions version 0.9-11 Index]