ggplot: how to specify vertical order of multiple boxplots?

Question

I would like to change the stacking order of hospitals in the diagram below so #1 is at the top and #4 at the bottom.

The diagram was produced with

ggplot(survey,aes(x=hospital, y=age))+geom_boxplot()+coord_flip()+xlab("")+ylab ("\nPatient Age")

and I need the top->down order to be the reverse of what is now. I'm not sure why it comes the way it does now. The 'hospital' column is a factor in case it matters.

Many thanks!

Answer 1

You have a few options. The easiest would be to add

p + scale_x_reverse()

to the plot. You could also reverse the levels of the factor

relevel(survey$hospital, rev(levels(survey$hospital))) -> survey$hospital

Or, you could determine the order you want the boxes by hand with xlim()

p + xlim("Hospital #4","Hospital #3","Hospital #2","Hospital #1")