How can I change the legend key size when I have a wrapped label?-CodePudding

I'm making a plot with a long legend label, and I'd like to resize the fill key so that it is square (i.e. does not extent to the top and bottom of the label text). I can use theme() or guide_legend() to make the legend key height as tall as I want, but I can't get it to be any smaller than the height of the wrapped text. Is there a way to override this minimum dimension?

Minimal code example included-- the first one successfully makes the key tall, but the second one fails to make the key short (which is what I want to happen).

theme_set(theme_bw())
df <- data.frame(x = rnorm(100))

ggplot(df)   
  geom_histogram(
    aes(x = x, fill = 'this text is \nway too long to \nfit on one line'))   
  theme(legend.key.height = unit(50, 'mm'))

ggplot(df)   
  geom_histogram(
    aes(x = x, fill = 'this text is \nway too long to \nfit on one line'))   
  theme(legend.key.height = unit(0.001, 'mm'))

CodePudding user response：

I'm not aware of a way to do this natively. I think your two options are either to go down the route of writing your own draw key, as in the link Stefan supplied, or try something a bit simpler but more of a hack, like this:

legend_height <- 8

ggplot(df)   
  geom_histogram(
    aes(x = x, fill = 'this text is \nway too long to \nfit on one line'),
    key_glyph = draw_key_path)   
  guides(fill = guide_legend(override.aes = list(
    size = legend_height, colour = "#f8766d")))

Or, with legend_height <- 2, you get: