How do I make my facets perfectly square?

Question

I'm using facet_wrap with ggplot to create a plot of facets. My problem is that my facets always come out looking like very short, very wide rectangles, but I want them to be square so they are easier to understand. Ideally, I would like to specify the number of columns I desire, and have ggplot figure out what the height of the plot should be so that all the facets are square. Is this possible?

Answer 1

Maybe aspect.ratio helps:

df <- data.frame(x = runif(100, 0,10), y = runif(100, 0, 50), z=gl(4,25))
ggplot(df, aes(x, y)) + 
  geom_point() + 
  facet_wrap(~ z, ncol = 4) + 
  theme(aspect.ratio = 1) # try with and without