How to make the bins line up in ggplot2?

Question

I used ggplot2 to plot a histogram shown below. I set the width of the bin into 5 or 10. However, the first bin in the chart seems to be only half of the bin width. 5-2.5 and 10-5. What caused this problem and how can I solve it?

Answer 1

You can control how bins line up with the center and boundary parameters. In this case, you probably want boundary = 0

library(ggplot2)

df <- data.frame(x = rnorm(100)*10)
ggplot(df, aes(x)) +
   geom_histogram(binwidth = 5, boundary = 0, color = "black", fill = "red")