[R] changing the limits of a secondary y-axis in a barplot

[Anna.Richards at csiro.au]

Hi,

I hope this is a simple question. I am having trouble changing the scale of a secondary y-axis on a barplot. When I run the code below the limits set for the first axis are always applied to the second axis as well. I am using the latest R version 2.12.0.


For example, if I have 3 vectors (Y1, Y2, Y3), and Y1 and Y2 need to be plotted on the left axis and Y3 on the right axis:
Y1<-c(7,10)
Y2<-c(8,11)
Y3<-c(1,2.5)

par(mfrow=c(1,1), mai=c(1.0,1.0,1.0,1.0))
Plot1<-barplot(rbind(Y1,Y2), beside=T, axes=T, names.arg=c("a","b"),
       ylim=c(0,15), xlim=c(1,9), space=c(0,1), col=c("darkgray","white"))
Plot2<-barplot(Y3, add=T, beside=T, names.arg="c",
       col=c("darkgray","white"), ylim=c(0,5), space=c(0,7), width=1)
axis(side=4)

How can I change the barplot so that the left hand axis scales from 0 to 15 and the right hand axis from 0 to 5?

Thank you,

Anna