Histogram only for non-missing values

[Asaf Yancu]

Dear Statalists,
My dataset contains duration in minutes of exams in multiple subjects.
I want to graph the frequency of every duration by each subject.
For example, when I tabulate duration if the subject is math

tab duration if subject==math,mi

I get

duration in |
    minutes |      Freq.     Percent        Cum.
------------+-----------------------------------
         75 |    255,844       23.32       23.32
         90 |    127,314       11.61       34.93
        105 |    165,198       15.06       49.99
        120 |     66,312        6.05       56.04
        180 |    307,021       27.99       84.03
        195 |          1        0.00       84.03
        255 |          3        0.00       84.03
        360 |          1        0.00       84.03
        435 |          1        0.00       84.03
          . |    175,219       15.97      100.00
------------+-----------------------------------
      Total |  1,096,914      100.00

When I use histogram for this propose:

hist duration if subject =="math"

I get this histogram

As you can see, for one that does not have the tabulate output for above from the duration variable, it is very hard to what are the values around 100.
Thus, I want my histogram to present only the listed values of duration and specify them.
It should look like this:

Many Thanks!

[Clyde Schechter]

I believe adding the -discrete- option to your -histogram- command will produce what you want.

[Nick Cox]

The combination of very high and very low frequencies is challenging here -- and I have sympathy with any position that a table serves very well.

Otherwise here are a few ideas.

* Example generated by -dataex-. For more info, type help dataex
clear
input int duration long frequency
 75 255844
 90 127314
105 165198
120  66312
180 307021
195      1
255      3
360      1
435      1
end


gen zero = 0
levelsof duration, local(levels)
gen toshow = cond(freq > 1e3, strofreal(round(freq/1000)) + "K", strofreal(freq))
spikeplot duration [fw=frequency],  addplot(scatter zero frequency duration, ms(Oh none) mlabel(. toshow) mlabpos(. 12)) ///
xla(`levels', labsize(small)) yla(none) legend(off) ysc(r(. 320e3) titlegap(*5)) xsc(r(60 450)) xtitle(Duration (minutes))

[Asaf Yancu]

Thank you Nick!