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 |

`as` |
an rmult object previously obtained with any compositional transformation of this package. |

`y` |
for both |

### 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))
```

*compositions*version 2.0-8 Index]