r - How to increase the size of points in legend of ggplot2?

Question

I have thousands of points in one figure and set the "size = 1". However the point size in the legend is reduced too. How to increase the point size in the legend?

For example.

num <- 10000
set.seed(1)
df <- data.frame(x = seq(1, num), y = runif(num), z = rep(1:2, each = num / 2))
df$z <- factor(df$z)
library(ggplot2)
p <- ggplot(df, aes(x, y, colour = z)) + geom_point(size = 1)
p

Answer 1

Add a + guides(colour = guide_legend(override.aes = list(size=10))) to the plot. You can play with the size argument.