compositions (version 0.9-11)

cdt: Centered default transform

Description

Compute the centered default transform of a (dataset of) composition or amount.

Usage

cdt(x)
          ## S3 method for class 'default':
cdt( x )
          ## S3 method for class 'acomp':
cdt( x )
          ## S3 method for class 'rcomp':
cdt( x )
          ## S3 method for class 'aplus':
cdt( x )
          ## S3 method for class 'rplus':
cdt( x )
          ## S3 method for class 'rmult':
cdt( x )
          ## S3 method for class 'factor':
cdt( x )

Arguments

x

a classed amount or composition (or a matrix of), to be transformed with its centered default transform

Value

• A corresponding matrix or vector containing the transforms.

Details

The general idea of this package is to analyse the same data with different geometric concepts as similar as possible. For each of the four concepts there exists a unique transform expressing the geometry in a linear subspace, keeping the relation to the variables. This unique transformation is computed by cdt. For acomp the transform is clr, for rcomp it is cpt, for aplus it is ilt, and for rplus it is iit. Each component of the result is identified with a unit vector in the direction of the corresponding component of the original composition or amount. Keep in mind that the transform is not necessarily surjective and thus variances in the image space might be singular.

See Also

idt, clr, cpt, ilt, iit

Examples

# the cdt is defined by
cdt         <- function(x) UseMethod("cdt",x)
cdt.default <- function(x) x
cdt.acomp   <- clr 
cdt.rcomp   <- cpt 
cdt.aplus   <- ilt 
cdt.rplus   <- iit
cdt(acomp(1:5))
cdt(rcomp(1:5))