Question

Creating the following plot results in the legend being placed vertically, on the right, rather than on the bottom horizontally as indicated in the call to opts():

dat <- data.frame(x = runif(10), y = runif(10), 
                  grp = rep(letters[1:2],each = 5))

ggplot(data = dat, aes(x = x, y = y, colour = grp)) + 
  geom_point() + 
  opts(legend.position = "bottom", legend.direction = "horizontal") + 
  theme_bw()

How do I get the legend in the correct spot?

Answer 1

The problem is that that theme_bw() is placed after the call to opts(), and resets some defaults. Just place theme_bw() before opts():

ggplot(data = dat, aes(x = x, y = y, colour = grp)) + 
  geom_point() + 
  theme_bw() +
  opts(legend.position = "bottom", legend.direction = "horizontal")

Note: Since version 0.9.2 opts has been replaced by theme:

theme(legend.position = "bottom", legend.direction = "horizontal")