R: {ggplot2}: How / Can I independently adjust the x-axis limits on a facet_grid plot?

I created a faceted set of three univariate densities -- comparing MCMC meth开发者_高级运维ods. Shown below

For the moment, I don't care about the tails. So how can I change the x-axis limits on the plots above to be:

c(-3,1)
c(-2,0)
c(-10, -8)

Is this even possible? I've already read this thread from 2009, but it doesn't seem to work. Was this implemented?

You can always allow limits to be set independently for each facet by specifying

+ facet_wrap(...,scales = "free_x")

There are also "free" and "free_y" options.