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boxplot {base}R Documentation

Box Plots

Description

Produce box-and-whisker plot(s) of the given (grouped) values.

Usage

boxplot(x, ...)
boxplot.default(x, ..., range = 1.5, width = NULL,
        varwidth = FALSE, notch = FALSE, names, boxwex = 0.8,
        data = sys.frame(sys.parent()), plot = TRUE,
        border = par("fg"), col = NULL, log = "", pars = NULL)
boxplot.formula(formula, data = NULL, subset, na.action, ...)

Arguments

x

an R object.

...

methods may have additional arguments.

x, ...

the data from which the boxplots are to be produced. The data can be specified as separate vectors, each corresponding to a component boxplot, or as a single list containing such vectors. Alternatively a symbolic specification of the form x ~ g can be given, indicating that the observations in the vector x are to be grouped according to the levels of the factor g. In this case the argument data can be used to provide values for the variables in the specification. NAs are allowed in the data.

range

this determines how far the plot whiskers extend out from the box. If range is positive, the whiskers extend to the most extreme data point which is no more than range times the interquartile range from the box. A value of zero causes the whiskers to extend to the data extremes.

width

a vector giving the relative widths of the boxes making up the plot.

varwidth

if varwidth is TRUE, the boxes are drawn with widths proportional to the square-roots of the number of observations in the groups.

notch

if notch is TRUE, a notch is drawn in each side of the boxes. If the notches of two plots do not overlap then the medians are significantly different at the 5 percent level.

names

group labels which will be printed under each boxplot.

boxwex

a scale factor to be applied to all boxes. When there are only a few groups, the appearance of the plot can be improved by making the boxes narrower.

data

data.frame, list, or environment in which variable names are evaluated when x is a formula.

plot

if TRUE (the default) then a boxplot is produced. If not, the summaries which the boxplots are based on are returned.

border

an optional vector of colors for the outlines of the boxplots. The values in border are recycled if the length of border is less than the number of plots.

col

if col is non-null it is assumed to contain colors to be used to col the bodies of the box plots.

log

character indicating if x or y or both coordinates should be plotted in log scale.

pars, ...

graphical parameters can also be passed as arguments to boxplot.

formula

a formula, such as y ~ x.

data

a data.frame (or list) from which the variables in formula should be taken.

subset

an optional vector specifying a subset of observations to be used in the fitting process.

na.action

a function which indicates what should happen when the data contain NAs.

...

further arguments to the default boxplot method and graphical parameters may also be passed as arguments, see par.

Details

This is a generic function. It currently has a default method (boxplot.default) and a formula interface (boxplot.formula).

Value

List with the following components:

stats

a matrix, each column contains the extreme of the lower whisker, the lower hinge, the median, the upper hinge and the extreme of the upper whisker for one group/plot.

n

a vector with the number of observations in each group.

conf

a matrix where each column contains the lower and upper extremes of the notch.

out

the values of any data points which lie beyond the extremes of the whiskers.

group

a vector of the same length as out whose elements indicate which group the outlier belongs to

names

a vector of names for the groups

See Also

boxplot.stats which does the computation, bxp for the plotting, and stripplot for an alternative (with small data sets).

Examples

## boxplot on a formula:
data(InsectSprays)
boxplot(count ~ spray, data = InsectSprays, col = "lightgray")

data(OrchardSprays)
boxplot(decrease ~ treatment, data = OrchardSprays,
        log = "y", col="bisque")

## boxplot on a matrix:
mat <- cbind(Uni05 = (1:100)/21, Norm = rnorm(100),
             T5 = rt(100, df = 5), Gam2 = rgamma(100, shape = 2))
boxplot(data.frame(mat), main = "boxplot(data.frame(mat), main = ...)")
[Package base version 1.1 ]