plotrix (version 3.8-2)

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,main="",xlim=NULL,lylim=NULL,rylim=NULL,
 mar=c(5,4,4,4),lcol=1,rcol=2,xlab="",lytickpos=NA,ylab="",ylab.at=NA,
 rytickpos=NA,rylab="",rylab.at=NA,lpch=1,rpch=2,
 type="b",xtickpos=NULL,xticklab=NULL,halfwidth=0.4,axislab.cex=1,
 do.first=NULL,xaxt="s",...)

Value

nil

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

main

Title for the plot

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

X axis label as in plot

lytickpos

Optional positions for the left axis tick labels.

ylab

Left Y axis label as in plot

ylab.at

Optional position for the left Y axis label

rytickpos

Optional positions for the right axis tick labels.

rylab

Right Y axis label

rylab.at

Optional position for the right Y axis label

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.

do.first

Optional command(s) that will be executed immediately after the blank plot is displayed.

xaxt

Whether to display the x-axis - "n" = no.

...

additional arguments passed to plot and points.

Author

Jim Lemon (thanks to Christophe Dutang for the idea of using bars and lines in the same plot, Clair Crossupton for pointing out that dates on the x-axis weren't very good, Jacob Kasper for the axis character expansion and Ye Lin for finally motivating me to add the do.first argument.)

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 overplotted.

Note that more values can be added to the plot using points or lines, but remember that these will be plotted relative to the left ordinate.

The do.first argument is useful for adding a background color or grid to the plot as shown in the first two examples.

See Also

plot

Examples

 xval1 <- seq.Date(as.Date("2017-01-02"),
  as.Date("2017-01-10"), by="day")
 xval2 <- seq.Date(as.Date("2017-01-01"),
  as.Date("2017-01-15"), by="day")
 going_up<-seq(3,7,by=0.5)+rnorm(9)
 going_down<-rev(60:74)+rnorm(15)
 twoord.plot(2:10,going_up,1:15,going_down,xlab="Sequence",
  ylab="Ascending values",rylab="Descending values",lcol=4,
  main="Plot with two ordinates - points and lines",
  do.first="plot_bg();grid(col=\"white\",lty=1)")
 axis.Date(1,xval2)
 # now separate the lines
 twoord.plot(2:10,going_up,1:15,going_down,xlab="Sequence",
  lylim=range(going_up)+c(-1,10),rylim=range(going_down)+c(-10,2),
  ylab="Ascending values",ylab.at=5,rylab="Descending values",
  rylab.at=65,lcol=4,main="Plot with two ordinates - separated lines",
  lytickpos=3:7,rytickpos=seq(55,75,by=5),
  do.first="plot_bg();grid(col=\"white\",lty=1)")
 twoord.plot(2:10,going_up,1:15,going_down,xlab="Sequence",
  lylim=range(going_up)+c(-1,10),rylim=range(going_down)+c(-10,2),
  type=c("bar","l"),ylab="Ascending values",ylab.at=5,
  rylab="Descending values",rylab.at=65,
  main="Bars on left axis, lines on right axis",
  lytickpos=3:7,rytickpos=seq(55,75,by=5),
  lcol=3,rcol=4,do.first="plot_bg()")
 twoord.plot(2:10,going_up,1:15,going_down,xlab="Sequence",
  lylim=c(-3,8),rylim=c(50,100),type=c("l","bar"),
  ylab="Ascending values",rylab="Descending values",
  lytickpos=3:7,rytickpos=seq(55,75,by=5),ylab.at=5,rylab.at=65,
  main="Lines on left axis, bars on right axis",
  lcol=3,rcol=4,do.first="plot_bg(\"yellow\")")
 # histogram with density curve superimposed
 xhist<-hist(rnorm(100),plot=FALSE)
 xdens<-dnorm(seq(-3,3,by=0.05))
 twoord.plot(xhist$mids,xhist$counts,seq(-3,3,by=0.05),
 xdens,type=c("bar","l"),lcol=4,rcol=2,ylab="Counts",
 rylab="Density",main="Histogram and density curve",
 halfwidth=0.2,lylim=c(0,max(xhist$counts)+1),rylim=c(0,0.45),lwd=2)