stacked area chart with no y variable ggplot2

Question

I need to create a stacked area chart with the following dataset (example):

ds <- data.frame(
  Time = c(rep(1, 4), rep(2, 4)),
  Type = c("a", "c", "f", "f", "e", "q", "a", "c")
)

I know the formula should be:

ggplot(ds, aes(x=time, y=???, fill=Type)) +
  geom_area()

My question is what do I put in the y value to have the count or the proportion of Type elements for each given Time?

Answer 1

You can count the occurrences of different Types at each Time point, then map that variable to the y-axis.

Data set

set.seed(123)
ds <- data.frame(
  Time = rep(1:10, each = 50),
  Type = sample(LETTERS[1:6], 500, replace = TRUE, prob = c(0.1,0.15,0.2,
                                                       0.1,0.25,0.2))
)

Count and plot

library(ggplot2)
library(dplyr)

ds |>
  count(Time, Type) |>
  ggplot(aes(x = Time, y = n, fill = Type)) +
  geom_area()

^{Created on 2024-04-05 with reprex v2.0.2}