# Confidence ellipses around categories

The *plotellipses()* function draws confidence ellipses around the categories of several categorical variables.

## Objectives

The objective is to see whether the categories of a categorical variable are significantly different from each other.

We are going to use the data set "tea" and draw confidence ellipses for four categorical variables: *"where"*, *"price"*, *"sex"* and *"age_Q"*.

## plotellipses

First load the package and the data set by typing:
`library(FactoMineR)`

data(tea)

Then perform an MCA:
`res.mca = MCA(tea, quanti.sup=19, quali.sup=c(20:36))`

Then launch the *plotellipses()* function:
`plotellipses(res.mca,keepvar=c("where","price","sex","age_Q"))`

`#res.mca: an object of class MCA`

#keepvar: a boolean or numeric vector of indexes of variables or a character vector of names of variables

Categories of *"sex"* and *"where"* are significantly different from each other.

For *"age_Q"* variable, the category *"15-24"* is significantly different from the others and other categories are not significantly different from each other.

For *"price"* variable, *"p_upscale*" and *"p_variable"* are significantly different from the others and from each other whereas other categories are not significantly different from each other.