Remove space between bars in ggplot2 geom_bar

Question

I am looking to "dodge" the bars of a barplot together. The following R code leaves white space between the bars. Other answers like this one show how to accomplish this for the bars part of a group, but that does not seem to apply for distinct bars per factor on the x axis.

require(ggplot2)
dat <- data.frame(a=c("A", "B", "C"), b=c(0.71, 0.94, 0.85), d=c(32, 99, 18))

ggplot(dat, aes(x= a, y = b, fill=d, width = d/sum(d))) +
  geom_bar(position=position_dodge(width = 0.1), stat="identity")

Playing with the width variable changes the appearance, but it does not seem possible to get the bars to sit side by side while still retaining their meaningful difference in width (in this graph redundantly represented by the fill colour too).

The problem could be that this would lead to uneven distances between x axis breaks. — erc
I would go even further and say it is impossible because of the uneven distances. I would try barplot() in this case. — ottlngr
@beetroot that seems to be the whole idea - can you control the position of factors as aesthetics on the X-axis? — Spacedman
@Spacedman yes, I am just not sure if that's a good way to visualise data - including information in the bar widths, has a bit of a pie-chart-feel to me.. — erc
@beetroot -- I agree with you, with one caveat. Having the widths vary definitely violates the area rule. However, if the x-axis width is meaningful, there is an argument that it should affect the area. Stripcharts do this (likely better than this solution), and provide useful information in two dimensions. I have a generally bad feeling about this particular example; but without a real world use case, it's hard to judge. I've answered with what is possible, not necessarily what is wise. OP: you may want to edit the post with information on why you want to do this to help future readers. — Mark Peterson

Mark Peterson Mark Peterson · Accepted Answer · 2017-01-31T13:24:47

I would generate my x-positions and widths first, then pass them in to the aesthetics and override to make your factor labels:

First, store the width

dat$width <-
  dat$d / sum(dat$d)

Then, assuming that your data.frame is in the order you want it plotted, you can set the location as the cumulative sum of the widths. Note, however, that that cumulative sum is where you want the right edge of the bar to be, so to get the center you need to subtract half of the width:

dat$loc <-
  cumsum(dat$width) - dat$width/2

Then, pass it all in to the ggplot call, setting your labels explictly:

ggplot(dat, aes(x= loc, y = b, fill=d, width = width)) +
  geom_bar(stat="identity") +
  scale_x_continuous(breaks = dat$loc
                     , labels = dat$a)

gives

I am not sure about the advisability of this appproach, but this should get the job done.

Remove space between bars in ggplot2 geom_bar

2 Answers