centipede.plot {plotrix}R Documentation

Display a centipede plot


Displays a centipede plot on the current graphics device.




segs a matrix of midpoints and limits calculated by get.segs OR a dstat object returned by brkdn.
mct 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. The default NA displays a text label showing the midpoint and limit functions.
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.


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. If a dstat object is passed as segs, the function will calculate the lower and upper values according to the relevant arguments. This type of plot is also known as a caterpillar plot or a league table.




Jim Lemon

See Also



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

[Package plotrix version 2.6-1 Index]