[R] Plot 2 time series with different y axes (left and right)

[Ajay Shah]

Petr Pikal said:

> I am not really a R specialist but for this task I use function:

and he pasted his code into the email. I reindented the code, and
wrote a fragment to experiment with it. Here it is:

---------------------------------------------------------------------------

plot.yy <- function(x, yright, yleft,
                    yleftlim=NULL, yrightlim = NULL,
                    xlab = NULL, yylab=c("",""),
                    pch=c(1,2), col=c(1,2),
                    linky=F, smooth=0,
                    lwds=1, length=10, format="%d-%H:%M", ...
                    )
{
  par(mar=c(5,4,4,2),oma=c(0,0,0,3))

  plot(x, yright, ylim=yrightlim, axes=F,ylab="", xlab=xlab,
       pch=pch[1],col=col[1], ...)
  axis(4,pretty(range(yright,na.rm=T),10),col=col[1])
  if (linky) lines(x,yright,col=col[1], ...)
  if (smooth!=0) lines(supsmu(x,yright,span=smooth),col=col[1], lwd=lwds, ...)
  if(yylab[1]=="")
    mtext(deparse(substitute(yright)),side=4,outer=T,line=1, col=col[1], ...)
  else
    mtext(yylab[1],side=4,outer=T,line=1, col=col[1], ...)

  par(new=T)
  plot(x,yleft, ylim=yleftlim, ylab="", axes=F ,xlab=xlab,
       pch=pch[2],col=col[2], ...)
  box()
  axis(2,pretty(range(yleft,na.rm=T),10),col=col[2], col.axis=col[2])

  if (is.null(class(x)))
    axis(1,pretty(range(x,na.rm=T),10))
  else {
    l<-length(x)
    axis(1,at=x[seq(1,l,length=length)],
         labels=format(as.POSIXct(x[seq(1,l,length=length)]),
           format=format))
  }

  if(yylab[2]=="")
    mtext(deparse(substitute(yleft)),side=2,line=2, col=col[2], ...)
  else
    mtext(yylab[2],side=2,line=2, col=col[2], ...)
  if (linky)
    lines(x,yleft,col=col[2], lty=2, ...)
  if (smooth!=0)
    lines(supsmu(x,yleft,span=smooth),col=col[2], lty=2, lwd=lwds, ...)
}

# I wrote some code in order to try out the plot.yy() function --
x = 1990:2000;
y1 = 100*rnorm(11)
y2 = 200*rnorm(11)
plot.yy(x, y1, y2, yylab=c("Y axis 1", "Y axis 2"),
        linky=T, smooth=0,
        lwds=3, length=10)

---------------------------------------------------------------------------

Thanks! This gave me lots of ideas.

When I run this code, I get the error --

Error in as.POSIXct.default(x[seq(1, l, length = length)]) : 
  Don't know how to convert `x[seq(1, l, length = length)]' to class "POSIXct"
Execution halted

I also find that one of the two series is not `linked' (in your
notation). I also find that the y label "Y axis 2" does not appear.
Any ideas?

Thanks again,

          -ans.

-- 
Ajay Shah                                                   Consultant
ajayshah at mayin.org                      Department of Economic Affairs
http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi