R: Automatic common backtransformation for compositions

backtransform {compositions} | R Documentation

## Automatic common backtransformation for compositions

### Description

Functions to automatically determine and compute the relevant back-transformation for a rmult object.

### Usage

              backtransform(x, as=x)
              backtransform.rmult(x, as=x)
              gsi.orig(x,y=NULL)
              gsi.getV(x,y=NULL)

### Arguments

`x` | an rmult object to be backtransformed; for both `gsi.*` functions: an rmult object to extract the relevant information from
`as` | an rmult object previously obtained with any compositional transformation of this package.
`y` | for both `gsi.*` functions: an alternative object to extract the relevant information from, in case that `x` does not include it

### Details

The general idea of this package is to analyse the same data with different geometric concepts, in a fashion as similar as possible. For each of the four concepts there exists a family of transforms expressing the geometry in aan appropriate manner. Transformed data can be further analysed, and certain results may be back-transformed to the original scale. These functions take care of tracking, constructing and computing the inverse transformation, whichever was the original geometry and forward transformation used.

### Value

For functions `backtransform` or `backtransform.rmult`, a corresponding matrix or vector containing the backtransformation of `x`. Efforts are taken to keep any extra attributes (beyond, "dim", "dimnames" and "class") the argument "x" may have \ For function `gsi.orig`, the original data with a compositional class, if it exists (or NULL otherwise). \ For function `gsi.getV`, the transposed, inverse matrix of log-contrasts originally used to forward transform the original composition `orig` to its coefficients/coordinates. If it does not exists, the output is NULL.

### Author(s)

R. Tolosana-Delgado, K.Gerald v.d. Boogaart http://www.stat.boogaart.de

### References

van den Boogaart, K.G. and R. Tolosana-Delgado (2008) "compositions": a unified R package to analyze Compositional Data, Computers & Geosciences, 34 (4), pages 320-338, doi: 10.1016/j.cageo.2006.11.017.

### See Also

`cdt`, `idt`, `clr`, `cpt`, `ilt`, `iit`, `ilr`, `ipt`, `alr`, `apt`

### Examples

    x <- acomp(1:5)
    x
    backtransform(ilr(x))
    backtransform(clr(x))
    backtransform(idt(x))
    backtransform(cdt(x))
    backtransform(alr(x))

[Package compositions version 2.0-2 Index]