Question

I have some problems with making a stacked bar chart in ggplot2. I know how to make one with barplot(), but I wanted to use ggplot2 because it’s very easy to make the bars have the same height (with ‘position = ‘fill”, if I’m not mistaken).

My problem is that I have multiple variables that I want to plot on top of each other; my data looks like this:

dfr <- data.frame(
  V1 = c(0.1, 0.2, 0.3),
  V2 = c(0.2, 0.3, 0.2),
  V3 = c(0.3, 0.6, 0.5),
  V4 = c(0.5, 0.1, 0.7),
  row.names = LETTERS[1:3]
)

What I want is a plot with categories A, B, and C on the X axis, and for each of those, the values for V1, V2, V3, and V4 stacked on top of each other on the Y axis. Most graphs that I have seen plot only one variable on the Y axis, but I’m sure that one could do this somehow.

How could I do this with ggplot2? Thanks!

Answer 1

First, some data manipulation. Add the category as a variable and melt the data to long format.

dfr$category <- row.names(dfr)
mdfr <- melt(dfr, id.vars = "category")

Now plot, using the variable named variable to determine the fill colour of each bar.

library(scales)
(p <- ggplot(mdfr, aes(category, value, fill = variable)) +
    geom_bar(position = "fill", stat = "identity") +
    scale_y_continuous(labels = percent)
)

(EDIT: Code updated to use scales packages, as required since ggplot2 v0.9.)