ggplot2: Adjust the symbol size in legends

Question

How should I change the size of symbols in legends? I checked the document of theme but found no answer.

Here is an example:

library(gg         


        

Answer 1

Marius's answer did not work for me as of R version 3.2.2. You can still call guide_legend() with the same override.eas argument but you will need to specify color instead of shape in the wrapper function.

So if you're running a later version of R, try this instead:

g + guides(color = guide_legend(override.aes = list(size=5)))

EDIT

As pointed out by @Ibo in the comment, this may have been due to the color scale in the ggplot object. If the ggplot object has contains a color scale, the mapping of size (size=5) has to be set on the color instead.