# R: Boxplots With Point Identification

Boxplot {car} | R Documentation

## Boxplots With Point Identification

### Description

`Boxplot` is a wrapper for the standard R `boxplot` function, providing point identification, axis labels, and a formula interface for boxplots without a grouping variable.

### Usage

    Boxplot(y, ...)

    ## Default S3 method:
    Boxplot(y, g, id=TRUE, xlab, ylab, ...)

    ## S3 method for class 'formula'
    Boxplot(formula, data=NULL, subset, na.action=NULL,
        id=TRUE, xlab, ylab, ...)

    ## S3 method for class 'list'
    Boxplot(y, xlab="", ylab="", ...)

    ## S3 method for class 'data.frame'
    Boxplot(y, id=TRUE, ...)

    ## S3 method for class 'matrix'
    Boxplot(y, ...)

### Arguments

`y` | a numeric variable for which the boxplot is to be constructed; a list of numeric variables, each element of which will be treated as a group; a numeric data frame or a numeric matrix, each of whose columns will be treated as a group.
`g` | a grouping variable, usually a factor, for constructing parallel boxplots.

`id`

a list of named elements giving one or more specifications for labels of individual points ("outliers"): `n`, the maximum number of points to label (default 10); `location`, `"lr"` (left or right) of points or `"avoid"` to try to avoid overplotting; `method`, one of `"y"` (automatic, the default), `"identify"` (interactive), or `"none"`; `col` for labels (default is the first color in `carPalette()` ); and `cex` size of labels (default is `1`). Can be `FALSE` to suppress point identification or `TRUE` (the default) to use all defaults. This is similar to how `showLabels` handles point labels for other functions in the car package, except that the usual default is `id=FALSE`.

`xlab, ylab` | text labels for the horizontal and vertical axes; if missing, `Boxplot` will use the variable names, or, in the case of a list, data frame, or matrix, empty labels.
`formula` | a ‘model’ formula, of the form `~ y` to produce a boxplot for the variable `y`, or of the form `y ~ g`, `y ~ g1*g2*...`, or `y ~ g1 + g2 + ...` to produce parallel boxplots for `y` within levels of the grouping variable(s) `g`, etc., usually factors.
`data, subset, na.action` | as for statistical modeling functions (see, e.g., `lm`).
`...` | further arguments, such as `at`, to be passed to `boxplot`.

### Author(s)

John Fox jfox@mcmaster.ca, with a contribution from Steve Ellison to handle `at` argument (see `boxplot`).

### References

Fox, J. and Weisberg, S. (2019) An R Companion to Applied Regression, Third Edition, Sage.

### See Also

`boxplot`

### Examples

    Boxplot(~income, data=Prestige, id=list(n=Inf)) # identify all outliers
    Boxplot(income ~ type, data=Prestige)
    Boxplot(income ~ type, data=Prestige, at=c(1, 3, 2))
    Boxplot(k5 + k618 ~ lfp*wc, data=Mroz)
    with(Prestige, Boxplot(income, id=list(labels=rownames(Prestige))))
    with(Prestige, Boxplot(income, type, id=list(labels=rownames(Prestige))))
    Boxplot(scale(Prestige[, 1:4]))

[Package car version 3.0-2 Index]