I would like to place two plots side by side using the ggplot2 package (ie. do the equivalent of par(mfrow=c(1,2))). For example, I would like to have the following two plots show side-by-side with the same scale.

x <- rnorm(100)
eps <- rnorm(100,0,.2)
qplot(x,3*x+eps)
qplot(x,2*x+eps)

Do I need to put them in the same data.frame like in this example?

qplot(displ, hwy, data=mpg, facets = . ~ year) + geom_smooth()

Thanks!