Display a boxplot with a gap (missing range)

Displays a boxplot with a missing range.

Usage

gap.boxplot(x,...,gap=list(top=c(NA,NA),bottom=c(NA,NA)),
 range=1.5,width=NULL,varwidth=FALSE,notch=FALSE,outline=TRUE,
 names,xlim=NA,ylim=NA,plot=TRUE,border=par("fg"),col=NULL,log="",
 axis.labels=NULL,axes=TRUE,pars=list(boxwex=0.8,staplewex=0.5,outwex=0.5),
 horizontal=FALSE,add=FALSE,at=NULL,main=NULL,xlab="",ylab="")

Arguments

x: numeric vector or a list of vectors
...: arguments passed to boxplot.
gap: the range(s) to be omitted - a list with two components, top and bottom each specifying a range to omit. The default range of c(NA,NA) means no omitted range
range: how far to extend the whiskers, (see boxplot)
width: the relative widths of the boxes
varwidth: if TRUE, box widths are proportional to the square roots of the number of observations
notch: whether to display the confidence intervals for the median as notches
outline: whether to display outliers
names: optional names to display beneath each boxplot
xlim,ylim: Optional x and y axis limits for the plot.
boxwex: scale factor for box widths
staplewex: staple width proportional to box width
outwex: outlier line width
plot: dummy argument for consistency with boxplot - always plots
border: optional color(s) for the box lines
col: optional color(s) to fill the boxes
log: whether to use a log scale - currently does nothing
axis.labels: Optional axis labels.
axes: Whether to display axes.
pars: optional parameters for consistency with boxplot
horizontal: whether to plot horizontal boxplots - currently does nothing
add: whether to add the boxplot(s) to an existing plot - currently does nothing.
at: optional horizontal locations for the boxplots.
main: a title for the plot.
xlab,ylab: X and Y axis labels.

Value

A list with the same structure as returned by boxplot, except that the values of elements beyond the gap(s) have their true positions on the plot rather than the original values. For example, in the second example, the value returned for the upper staple of the right boxplot is 14 rather than 20, due to the 6 unit gap.

Details

Displays boxplot(s) omitting range(s) of values on the top and/or bottom of the plot. Typically used when there are outliers far from the boxes. See boxplot for more detailed descriptions of the arguments. If the gaps specified include any of the values in the stats matrix returned from boxplot, the function will exit with an error message. This prevents generation of NAs in indexing operations, which would fail anyway. A gap can include part of a box, but it is unlikely that this would be intended by the user.

See axis.break for a brief discussion of plotting on discontinuous coordinates.

Author

Jim Lemon

Examples

 twovec<-list(vec1=c(rnorm(30),-6),vec2=c(sample(1:10,40,TRUE),20))
 gap.boxplot(twovec,gap=list(top=c(12,18),bottom=c(-5,-3)),
 main="Show outliers separately")

 if(dev.interactive()) par(ask=TRUE)
 gap.boxplot(twovec,gap=list(top=c(12,18),bottom=c(-5,-3)),range=0,
 main="Include outliers in whiskers")

 par(ask=FALSE)