Shade area between lines with ggplot2

Question

I want to shade the area between the grouped lines. I've tried different approaches but I don't manage to do it.

df <- data.frame(year = rep(c(1950:1955), each = 2),
                 gender = factor(rep(c("male", "female"), times = 6)),
                 value = c(40526812, 37450509, 43027405,
                            40135682, 45801088, 43130369,
                            48579427, 46077640, 50948574,
                            48493786, 53052094, 50537984))

df |> 
  ggplot(aes(year, value, group = gender)) +
  geom_line()

Thanks in advance!

Does this answer your question? [Shade region between two lines with ggplot](https://stackoverflow.com/questions/28586635/shade-region-between-two-lines-with-ggplot) — Adam Quek, Jul 22 '22 at 10:10

score 4 · Accepted Answer · answered Jul 22 '22 at 10:23

You could define the boundaries of the area by using a pivot_wider to create the ymax and ymin of the area in geom_ribbon so you don't need to subset per argument. So it will be easier to reproduce. Here an example:

df <- data.frame(year = rep(c(1950:1955), each = 2),
                 gender = factor(rep(c("male", "female"), times = 6)),
                 value = c(40526812, 37450509, 43027405,
                           40135682, 45801088, 43130369,
                           48579427, 46077640, 50948574,
                           48493786, 53052094, 50537984))

library(ggplot2)
library(dplyr)
library(tidyr)
area <- df %>%
  pivot_wider(names_from = gender, values_from = value) %>%
  mutate(
    ymax = pmax(male, female),
    ymin = pmin(male, female)
  )

ggplot(data = df, mapping = aes(year, y = value, group = gender)) +
  geom_line() +
  geom_ribbon(data = area, mapping = aes(year, ymin = ymin, ymax = ymax), alpha = 0.4, inherit.aes = FALSE )

^{Created on 2022-07-22 by the reprex package (v2.0.1)}

When inherit.aes if FALSE, it overrides the default aesthetics instead of combining them. This is useful because we use in this case two dataframes so we can define both the data and aesthetics so that is does not inherit the behaviour. — Quinten, Jul 22 '22 at 11:13

score 3 · Answer 2 · answered Jul 22 '22 at 10:20

You can use geom_ribon which allows to shade areas within axis values.
A stronger alpha will play on the shader intensity.

  ggplot(data=df, aes(year, value, group = gender)) +
  geom_line() + 
  geom_ribbon(data=subset(df, 1950 <= year & year <= 1955), 
              aes(ymin=rep(subset(df, gender=='female')$value, each=2), 
                  ymax=rep(subset(df, gender=='male')$value, each=2)), fill="blue", alpha=0.5)

Shade area between lines with ggplot2

2 Answers2