Using legend with stat_function in ggplot2

Question

I am using scale_colour_manual to specify the possible keys in the legend. However, if I use stat_function to plot custom function, the legend is m

Answer 1

Put colour= inside the aes() and then provide name for particular line as is should appear in legend. Legend is made for aesthetics that are only inside aes() call.

ggplot(my.df, aes(x=x)) +
  stat_function(fun = MyFun, n = 1000, args = list(p = 10), aes(colour = "line1")) +
  stat_function(fun = MyFun, n = 1000, args = list(p = 3), aes(colour = "line2")) +
  stat_function(fun = MyFun, n = 1000, args = list(p = 2), aes(colour = "line3")) +
  stat_function(fun = MyFun, n = 1000, args = list(p = 1), aes(colour = "line4")) +
  scale_colour_manual("Lgend title", values = c("red", "blue", "green", "orange"))