[R] Two x axes - top and bottom

[David Winsemius]

On Feb 8, 2014, at 2:57 PM, 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?

library(ggplot2)
library(gridExtra)

x <- qplot(mpg, disp, data = mtcars)
y <- qplot(hp, wt, data = mtcars)
grid.arrange(x,y)

-- 
David Winsemius
Alameda, CA, USA