Vertical line at forefront of histogram

[Maxence Morlet]

Hi all, data are below.

I wish to make a histogram of this variable. I would like to add a vertical line to the x-axis, and bring it at the forefront of the histogram.

The below code does everything, but does not bring the line at the forefront:

su mcq_exam_gap
hist mcq_exam_gap, w(1) xti("Differential MCQ Less Final Exam Grade") xline(`r(mean)') freq

How can I bring the line in front of the bars of the histogram?

clear
input float mcq_exam_gap
-10
  0
-12
-27
-15
 -1
-15
-15
  9
-11
  5
  7
 14
-44
 -2
 14
  3
 12
 -9
  0
  7
 10
 32
-20
  4
 -3
 -8
 -8
 53
 -1
-15
  1
 -5
  3
 15
 -5
 23
 -5
 18
 -3
  5
-14
  0
-24
-10
  4
 -8
  0
 -6
 -6
  8
 12
 -9
 -1
 15
-21
 -3
 19
 12
 13
 -7
  7
 17
-35
-28
 15
 -5
 -6
  0
  2
  5
 12
 -2
-13
  1
 -7
 -4
 -4
  3
 -2
 -2
 -2
-23
-15
 -7
 -7
  0
-13
 -6
 -5
-13
 -4
 -3
 -2
 -9
-14
-35
 -2
 -3
 -7
end

[Nick Cox]

hist mcq_exam_gap, w(1) xti("Differential MCQ Less Final Exam Grade") addplot(scatteri  0 `r(mean)' 8 `r(mean)', recast(line)) freq legend(off)

With that solution you do need two passes to work out "which value of 8" you need (to recycle an old joke attributed to William Feller).

For a miniature review in this territory see https://journals.sagepub.com/doi/pdf...6867X241276116 from Stata Journal 24(3) 2024 (that is, the latest issue).

[Maxence Morlet]

Thank you very much Dr. Cox! In my case, it was 100.

[Nick Cox]

A line is much easier to see on a quantile plot.

su mcq_exam_gap, meanonly 

local mean = r(mean)

* Stata Journal 
qplot mcq_exam_gap, yli(`mean') aspect(1) xla(0 0.25 "0.25" 0.5 "0.5" 0.75 "0.75" 1)

quantile mcq_exam_gap, yli(`mean') aspect(1) rlopts(lc(none))