Plot aggregate density with ggplot2

Question

I want to plot the a single line representing aggregate density by sex on this graph. In other words, I want to plot another layer that is the average of all the lines, grouped by sex. I tried my best to create a reproducible example, and came pretty close:

library(ggplot2)
A <- c(rnorm(2000, mean = 20, sd = 2), rnorm(2000, mean = 30, sd = 3))
B <- rep(c(1:100), 40)
C <- as.factor(c(rep(1, 2000), rep(2,2000)))

data <- data.frame("CT" = A, "ID" = B, "Sex" = C)

ggplot(data, aes(x=CT)) +
  geom_line(aes(color=Sex, group = interaction(ID, Sex)), stat="density", size=0.3, alpha=0.4)

phalteman · Accepted Answer · 2021-09-10 20:41:08Z

1

You can just add another geom_line() without the grouping variable, which will give what I think you're looking for:

ggplot(data, aes(x=CT)) +
  geom_line(aes(color=Sex, group = interaction(ID, Sex)), stat="density", size=0.3, alpha=0.4) +
  geom_line(stat="density")

which gives:

Or, if you still want average density of the lines within each Sex grouping, you can replace the last line above with:

geom_line(stat="density", aes(group=Sex), size=1.25)

or

geom_line(stat="density", aes(colour=Sex), size=1.25)

if you want the colours to match.

edited Sep 10, 2021 at 20:41

answered Aug 11, 2021 at 15:34

phalteman

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