plotrix (version 2.8-3)

twoord.plot: Plot with two ordinates

Description

Two sets of values are displayed on the same plot with different ordinate scales on the left and right.

Usage

twoord.plot(lx,ly,rx,ry,data=NULL,xlim=NULL,lylim=NULL,rylim=NULL,
 mar=c(5,4,4,4),lcol=1,rcol=2,xlab="",ylab="",rylab="",lpch=1,rpch=2,
 type="b",xtickpos=NULL,xticklab=NULL,halfwidth=0.4,axislab.cex=1,...)

Arguments

lx,ly,rx,ry

y and optional x values for the plot

data

an optional data frame from which to obtain the above values

xlim

optional x limits as in plot

lylim,rylim

optional y limits for the left and right axes respectively

mar

optional margin adjustment, defaults to c(5,4,4,4)

lcol,rcol

colors to distinguish the two sets of values

xlab,ylab

axis labels as in plot

rylab

label for the right axis

lpch,rpch

plot symbols to distinguish the two sets of values

type

as in plot

xtickpos

Optional positions for x-axis tick labels.

xticklab

Optional labels for x-axis. Useful for things like dates.

halfwidth

Half the width of the bars in user units. The bars are centered on successive integers if no x values are supplied.

axislab.cex

Character expansion for the axis labels and tick labels.

...

additional arguments passed to plot.

Value

• nil

Details

twoord.plot automates the process of displaying two sets of values that have different ranges on the same plot. It is principally useful in illustrating some relationship between the values across the observations. It is assumed that the lx and rx values are at least adjacent, and probably overlapping. It is best to pass all the arguments lx, ly, rx, ry, but the function will attempt to substitute sensible x values if one or two are missing.

If at least one of the type arguments is "bar", bars will be plotted instead of points or lines. It is best to plot the bars first (i.e. relative to the left axis) if the other type is points or lines, as the bars will usually obscure at least some of the points or lines. Using NA for the color of the bars will partially correct this. If both types are to be bars, remember to pass somewhat different x values or the bars will be overlaid.

See Also

plot

Examples

twoord.plot(2:10,seq(3,7,by=0.5)+rnorm(9),
  1:15,rev(60:74)+rnorm(15),xlab="Sequence",
  ylab="Ascending values",rylab="Descending values",
  main="Plot with two ordinates - points and lines")
 twoord.plot(2:10,seq(3,7,by=0.5)+rnorm(9),
  1:15,rev(60:74)+rnorm(15),xlab="Sequence",
  ylab="Ascending values",rylab="Descending values",
  main="Plot with two ordinates - bars on the left",
  type=c("bar","l"),lcol=3,rcol=4)
 twoord.plot(2:10,seq(3,7,by=0.5)+rnorm(9),
  1:15,rev(60:74)+rnorm(15),xlab="Sequence",
  ylab="Ascending values",rylab="Descending values",
  main="Plot with two ordinates - bars on the right",
  type=c("b","bar"),lcol=2,rcol=NA,halfwidth=0.2)
 # histogram with density curve overlaid
 xhist<-hist(rnorm(100),plot=FALSE)
 xdens<-dnorm(seq(-2,2,by=0.05))
 twoord.plot(xhist$mids,xhist$counts,seq(-2,2,by=0.05),
 xdens,type=c("bar","l"),lcol=4,rcol=2,ylab="Counts",
 rylab="Density",main="Histogram and density curve",
 halfwidth=0.2)