Create custom x-axis labels for hist()

Question

I am using the code below to create a histogram. I've tried replacing the x-axis values using the axis code, but nothing happens other than my x-axis ends up with no labels. Does anyone have any solutions?

 par(mfrow=c(3,1))
 for (i in c(10,20,30)) {
   a <- rnorm(50, 90, i)
   hist(a, breaks=10, main = i, xaxt="n")
   axis(1,at=seq(-2,2,by=1/3), labels =seq(-2,2,by=1/3))
   abline(v=i * seq(-2, 2, by = 1/3) + 90, col = rainbow(length(seq(-2,2,by=1/3))))
  }

Answer 1

You probably want a sequence in the range of the breaks with length of the length of your custom sequence. You may exploit the invisible return of hist.

set.seed(42)
op <- par(mfrow=c(3, 1))
for (i in c(10, 20, 30)) {
  a <- rnorm(50, 90, i)
  h <- hist(a, breaks=10, main=i, xaxt="n")
  sq <- round(seq(-2, 2, by=1/3), 2)
  ats <- do.call(seq, c(as.list(range(h$breaks)), length.out=length(sq)))
  axis(1, at=ats, labels=sq)
  abline(v=i * sq + 90, col=rainbow(length(sq)))
}
par(op)

Gives