R help - Nov 2010 - changing the limits of a secondary y-axis in a barplot

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

Hi Anna,
>> 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?
Try this:

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"),
yaxt="n")
Plot2<-barplot(Y3, add=T, beside=T, names.arg="c",
col=c("darkgray","white"), ylim=c(0,5), space=c(0,7),
width=1, yaxt="n")
axis(side=2, at=seq(0,15,3), labels=seq(0,15,3))
axis(side=4, at=seq(0,15,3), labels=seq(0,5,1))

Regards, Mark.
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On 11/17/2010 03:06 PM, Anna.Richards at csiro.au wrote:
> 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?
>
Hi Anna,
Have a look at the twoord.plot function in the plotrix package. This 
does exactly what you describe above.

Jim