在ggplot中结合填充和颜色图例

Question

I have found some Questions similar to my issue, but none that really fit. I have 4 data columns I want to plot, 3 as lines and 1 as area.

I'd like to condense the Legend of the resulting Plot into a neat 2 row, 2 column set-up, but I can't seem to figure out how. Example code:

library(tidyverse)

#Random Data
data <- tibble(X=1:50,
               A=sample(seq(5, 6, 0.1), 50, replace = TRUE),
               B=sample(seq(4, 5, 0.1), 50, replace = TRUE),
               C=sample(seq(3, 4, 0.1), 50, replace = TRUE),
               D=sample(seq(1, 3, 0.5), 50, replace = TRUE))

ggplot(data, aes(x=X)) + 
  geom_area(aes(y=D, fill='Dataset4'), alpha=0.5) + 
  geom_line(aes(y=A, color='Dataset1')) +
  geom_line(aes(y=B, color='Dataset2')) +
  geom_line(aes(y=C, color='Dataset3')) +
  ylab("")+
  guides(fill=guide_legend(nrow=2, order=2),
         color=guide_legend(nrow=2, order=1))

Resulting figure:

I'd like to have the four legend entries in a 2x2 orientation, is that even possible?

Answer 1

You can do that by using a scale that has colour and fill aesthetics. The tricky bit is letting the legend know what should be drawn as a line and what as a polygon, for which I don't have an automatic solution. The manual solution below works, though you'd have to replace the 4th fill with another colour if you use a different scale.

library(ggplot2)
library(tibble)

#Random Data
data <- tibble(X=1:50,
               A=sample(seq(5, 6, 0.1), 50, replace = TRUE),
               B=sample(seq(4, 5, 0.1), 50, replace = TRUE),
               C=sample(seq(3, 4, 0.1), 50, replace = TRUE),
               D=sample(seq(1, 3, 0.5), 50, replace = TRUE))

ggplot(data, aes(x=X)) + 
  geom_area(aes(y=D, fill='Dataset4'), alpha=0.5) + 
  geom_line(aes(y=A, color='Dataset1')) +
  geom_line(aes(y=B, color='Dataset2')) +
  geom_line(aes(y=C, color='Dataset3')) +
  scale_colour_discrete(
    name = "",
    aesthetics = c("colour", "fill"),
    guide = guide_legend(
      nrow = 2, override.aes = list(
        linetype = c(1, 1, 1, 0),
        fill = c(NA, NA, NA, scales::hue_pal()(4)[4])
      )
    )
  ) +
  ylab("")
#> Warning: Duplicated override.aes is ignored.

^{Created on 2022-08-31 by the reprex package (v2.0.0)}