Modify bin labels histogram

Question

I made the following histogram:

one <- c(2,2,3,3,3,3,4,4,4,4,4,4,5,5,5,5,6,6,7,8)
hist(one, breaks = 3)

Instead of a range from 2-8 on the x-axis, I need three labels on the x-axis that summarize the range of values like this: 2-3; 4-5; 6-8

How can I modify the code for the x-axis to get just three labels, and in the correct location?

Answer 1

It's easy to label midpoints for the ranges using:

h <- hist(one, breaks = 3, xaxt = 'n')
axis(1, h$mids, h$mids)

But if you want to have the labels be character strings naming the ranges, you have to do a little more work. Take a look at str(h) to see what you have to work with:

> str(h)
List of 6
 $ breaks  : num [1:4] 2 4 6 8
 $ counts  : int [1:3] 12 6 2
 $ density : num [1:3] 0.3 0.15 0.05
 $ mids    : num [1:3] 3 5 7
 $ xname   : chr "one"
 $ equidist: logi TRUE
 - attr(*, "class")= chr "histogram"

You can use the breaks element to construct axis labels:

h <- hist(one, breaks = 3, xaxt = 'n')
axis(1, h$mids, paste(h$breaks[1:3], h$breaks[2:4], sep=' - '))