Reverse stacked bar order

Question

I'm creating a stacked bar chart using ggplot like this:

plot_df <- df[!is.na(df$levels), ] 
ggplot(plot_df, aes(group)) + geom_bar(aes(fill = levels), position = "fill")

Which gives me something like this:

How do I reverse the order the stacked bars themselves, so that level 1 is at the bottom, and level 5 is at the top of each bar?

I've seen a number of questions on this (e.g. How to control ordering of stacked bar chart using identity on ggplot2) and the common solution seems to be to reorder the dataframe by that level as that what ggplot is using the determine the order

So I've tried reordering using dplyr:

plot_df <- df[!is.na(df$levels), ] %>% arrange(desc(levels))

However, the plot comes out the same. It also doesn't seem to make a difference whether I arrange by ascending or descending order

Here is a reproducible example:

group <- c(1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4)
levels <- c("1","1","1","1","2","2","2","2","3","3","3","3","4","4","4","4","5","5","5","5","1","1","1","1")
plot_df <- data.frame(group, levels)

ggplot(plot_df, aes(group)) + geom_bar(aes(fill = levels), position = "fill")

Aurelie

The order of the observations makes no sense, but the order of the factor levels does. Also, reprex. – Marquess

yes, I have also tried changing the factor level order with levels(plot_df$levels) <- c("1", "2", "3", "4", "5") (and the reverse order) but it doesn't change the graph order – Aurelie

Also added an example of the data – Aurelie

plot_df %>% mutate(levels = factor(levels, levels = 5:1)) %>% ggplot(aes(group, fill = levels)) + geom_bar(position = "fill") or just ggplot(plot_df, aes(group)) + geom_bar(aes(fill = levels), position = position_fill(reverse = TRUE)) – Marquess

Answer 1

The release notes of ggplot2 version 2.2.0 on Stacking bars suggest:

If you want to stack in the opposite order, try forcats::fct_rev()

library(ggplot2)   # version 2.2.1 used    
plot_df <- data.frame(group = rep(1:4, 6),
                      levels = factor(c(rep(1:5, each = 4), rep(1, 4))))
ggplot(plot_df, aes(group, fill = forcats::fct_rev(levels))) + 
  geom_bar(position = "fill")

This is the original plot:

ggplot(plot_df, aes(group, fill = levels)) + 
  geom_bar(position = "fill")

Or, using position_fill(reverse = TRUE) as suggested by alistaire in his comment:

ggplot(plot_df, aes(group, fill = levels)) + 
  geom_bar(position = position_fill(reverse = TRUE))

Note that the levels (colors) in the legend is not in the same order as in the stacked bars.

Prae

position_fill(reverse = TRUE) normalizes bars, use position_stack(reverse = TRUE) if you don't want to normalize bars. – Gymnasiast

Answer 2

An alternative is to reorder the factor as such, assuming the factor is called "levels": levels = ordered(levels, levels=c(5,4,3,2,1)). for more info: http://www.cookbook-r.com/Manipulating_data/Changing_the_order_of_levels_of_a_factor/

Landre