ggplot binwidth in R

Question

I have a question about the binwidth in ggplot in r.

I have two sets of data, one called "error_hat" and one called "error_tilde". I have made their histogram separately, and I see they are similar to each other.

enter image description here

Now I want to put them together to make a comparison. My code is as followed:

catagory <- c(rep("error_hat",length(error_hat)) , rep("error_tilde",length(error_tilde)))

error <- c(error_hat, error_tilde)

error_data<-data.frame(catagory,error)

ggplot(error_data, aes(x=error,group=catagory,fill=catagory))+
  geom_histogram(position="dodge2", binwidth=0.03)+theme_bw()

It produces a picture like this:

enter image description here

I am wondering why the data in the middle has a different width (since I have set all the width to be 0.03)?

Could anyone help me with this problem? Many thanks!

binwidth doesn't refer to the width of the bars as they appear on the chart, it refers to how your data is "binned" into groups to make a histogram. So binwidth = 0.03 means that, for example, values from 0 - 0.03 will be counted up to make one bar, and values from 0.03-0.06 will be counted up to make the 2nd bar, and so on. — divibisan
– divibisan, Commented Jan 16, 2019 at 1:09
Possible duplicate of Bars in geom_bar are not of equal width — divibisan
– divibisan, Commented Jan 16, 2019 at 1:11

Chase · Accepted Answer · 2019-01-16 02:56:37Z

1

This is a consequence of using dodge2 versus dodge. This is the expected behavior as outlined here.

Maybe you want regular dodge instead?

library(ggplot2)
#fake data that mimics yours
set.seed(42)
error_hat <- runif(100)
error_tilde <- runif(100)
catagory <- c(rep("error_hat",length(error_hat)) , rep("error_tilde",length(error_tilde)))
error <- c(error_hat, error_tilde)
error_data<-data.frame(catagory,error)
ggplot(error_data, aes(x=error,group=catagory,fill=catagory))+
  geom_histogram(position="dodge", binwidth=0.03)+theme_bw()

^{Created on 2019-01-15 by the reprex package (v0.2.1)}

answered Jan 16, 2019 at 2:56

Chase

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