# Functions and Methods for Correspondence Regression

### Description

This package provides functions and methods for performing correspondence regression, i.e. the correspondence analysis of the
crosstabulation of a categorical variable Y in function of another one X, where X can in turn be made up of the combination of various
categorical variables.
Consequently, correspondence regression can be used to analyze the effects for a polytomous or multinomial outcome variable.
The central function in the package is `corregp`

, which enables methods for printing, summarizing and plotting the output.
Additionally, there are functions for computing confidence intervals, ellipses or 3D ellipsoids (by means of bootstrapping).

### Contents

This package consists of the following datasets, functions, generics and methods:

#### Datasets

`HairEye`

Hair and eye color of statistics students (data frame).`COMURE`

The use of linguistic variants in translations vs. non-translations and in six different registers.`TSS`

The use of inflected or uninflected determiners in vernacular Belgian Dutch.

#### Functions

`ci`

A helper function to compute confidence intervals on the basis of a numeric vector.`confGet`

An internal function to retrieve the`conf`

components in a`corregp`

object.`corregp`

The basic function to perform correspondence regression. Typically, one starts here, and then one uses`print`

,`summary`

,`screeplot`

or`plot`

methods.

#### Generics

`cint`

Compute confidence intervals.`cell`

Compute confidence ellipses.`cell3d`

Compute 3D confidence ellipsoids.`ciplot`

Plot confidence intervals.`pcplot`

Plot parallel coordinates.

#### Methods

`print.corregp`

Print the output of a correspondence regression.`summary.corregp`

Give a`summary`

of a correspondence regression.`print.summary.corregp`

Print the`summary`

of a correspondence regression.`screeplot.corregp`

Make a scree plot on the basis of the output of a correspondence regression.`cint.corregp`

Compute confidence intervals on the basis of the output of a correspondence regression. Typically, this function is not so much used directly as it is called by a`ciplot.corregp`

command.`ciplot.corregp`

Plot confidence intervals on the basis of the output of a correspondence regression.`pcplot.corregp`

Make a parallel coordinate plot on the basis of the output of a correspondence regression.`cell.corregp`

Compute confidence ellipses on the basis of the output of a correspondence regression. Typically, this function is not so much used directly as it is called by a`plot.corregp`

command.`plot.corregp`

Plot the output (and the optional confidence ellipses) of a correspondence regression.`cell3d.corregp`

Compute 3D confidence ellipsoids on the basis of a correspondence regression. Typically, this function is not so much used directly as it is called by a`plot3d.corregp`

command.`plot3d.corregp`

Plot the 3D output (and the optional confidence ellipsoids) of a correspondence regression.

### Future prospects

Include a vignette.

Allow for more than one random factor (e.g. enable the argument

`parm`

to be a character vector of more than one element).Specify methods for

`anova`

,`predict`

,`residuals`

etc.Enable scale transformations for all plots (and corresponding confidence regions).

Provide the possibility for so-called "calibration lines".

### Author

Koen Plevoets, koen.plevoets@ugent.be

### Acknowledgements

This package has benefited greatly from the helpful comments of Isabelle Delaere and Gert De Sutter. Thanks to Kurt Hornik and Uwe Ligges for proofing this package.