plotrix (version 2.1-5)

centipede.plot: Display a centipede plot

Description

Displays a centipede plot on the current graphics device.

Usage

centipede.plot(segs,midpoint="mean",lower.limit="std.error",
  upper.limit="std.err",left.labels=NULL,right.labels=NULL,sort.segs=TRUE,
  main="",xlab="",vgrid=NA,mar=NA,col=par("fg"),bg="green",...)

Arguments

segs

a matrix of midpoints and limits calculated by get.segs.

midpoint

The function to use in calculating the midpoint of each segment.

lower.limit

The functions to use in calculating the lower limits for each subset of the data.

upper.limit

The functions to use in calculating the upper limits.

left.labels

The variable or subset labels to place at the left margin of the plot. Default values are provided.

right.labels

The variable or subset labels to place at the right margin of the plot.

sort.segs

Whether to sort the segments in ascending order.

main

Optional title for the plot.

xlab

Optional x axis label for the plot.

vgrid

Optional vertical line(s) to display on the plot.

mar

Margin widths for the plot. Defaults to c(4,5,1,4) or c(4,5,3,4) if there is a title.

col

The color(s) of the limit lines and borders of the midpoint markers.

bg

The color(s) to fill the midpoint markers.

...

additional arguments passed to plot.

Value

• nil.

Details

centipede.plot displays one or more midpoints and limits as filled circles with horizontal error bars. It places labels on the left and right sides of the plot. If these labels are long, it may be necessary to pass explicit values to the mar argument to leave enough room. Similarly, centipede plots typically have a large number of subsets, and it may be necessary to start the graphics device with an aspect ratio that will prevent crowding of the labels when over 30 segments are displayed. The matrix segs may be entered manually or read from a file. The first row specifies midpoints, the second and third rows the lower and upper limits respectively and the fourth row the number of valid observations.

See Also

get.segs

Examples

testcp<-list("",40)
 for(i in 1:40) testcp[[i]]<-rnorm(sample(1:8,1)*50)
 segs<-get.segs(testcp)
 centipede.plot(segs,main="Test centipede plot",vgrid=0)