[R] Two x axes - top and bottom

[Jim Lemon]

On 02/09/2014 09:57 AM, Benjamin Ward (ENV) wrote:
> Hi, fellow R users,
>
> I've been asked to make a plot with two datasets each with a different x axis, and it's been suggested one be at the top and the other at the bottom of the graph. I normally use ggplot2, and I know how to plot multiple datasets by simply + a new geom with a different data option, but usually in these case my different datasets have had the same x and y axes. Can I add a new x axis to the top of the plot in ggplot2 or one of the other graphics packages?
>
Hi Ben,
The basic method would be something like this:

plot(1:4,rnorm(4))
par(new=TRUE)
plot(c(10,20,30,40),rnorm(4),axes=FALSE)
axis(3,at=c(10,20,30,40))

Obviously you would need to do a bit of messing around with titles and 
axis labels, etc.

Jim