ggplot reorder stacked bar plot based on values in data frame

Question

I am making stacked bar plots with ggplot2 in R with specific bar ordering about the y-axis.

# create reproducible data
library(ggplot2)
d <- read.csv(text='Day,Location,Length,Amount
            1,4,3,1.1
            1,3,1,2
            1,2,3,4
            1,1,3,5
            2,0,0,0
            3,3,3,1.8
            3,2,1,3.54
            3,1,3,1.1',header=T)

ggplot(d, aes(x = Day, y = Length)) + geom_bar(aes(fill = Amount, order = Location), stat = "identity")

ggplot(d, aes(x = Day, y = Length)) + geom_bar(aes(fill = Amount, order = rev(Location)), stat = "identity")

The first ggplot plot shows the data in order of Location, with Location=1 nearest the x-axis and data for each increasing value of Location stacked upon the next.

The second ggplot plot shows the data in a different order, but it doesn't stack the data with the highest Location value nearest the x-axis with the data for the next highest Location stacked in the second from the x-axis position for the first bar column, like I would expect it to based on an earlier post.

This next snippet does show the data in the desired way, but I think this is an artifact of the simple and small example data set. Stacking order hasn't been specified, so I think ggplot is stacking based on values for Amount.

ggplot(d, aes(x = Day, y = Length)) + geom_bar(aes(fill = Amount), stat = "identity")

What I want is to force ggplot to stack the data in order of decreasing Location values (Location=4 nearest the x-axis, Location=3 next, ... , and Location=1 at the very top of the bar column) by calling the order = or some equivalent argument. Any thoughts or suggestions?

It seems like it should be easy because I am only dealing with numbers. It shouldn't be so hard to ask ggplot to stack the data in a way that corresponds to a column of decreasing (as you move away from the x-axis) numbers, should it?

@VeerendraGadekarm not really, I hadn't actually seen the use of the order aesthetic before. — BrodieG

BrodieG BrodieG · Accepted Answer · 2015-06-09T18:12:41

Try:

ggplot(d, aes(x = Day, y = Length)) + 
  geom_bar(aes(fill = Amount, order = -Location), stat = "identity")

Notice how I swapped rev with -. Using rev does something very different: it stacks by the value for each row you happen to get if you reverse the order of values in the column Location, which could be just about anything.

ggplot reorder stacked bar plot based on values in data frame

1 Answers