Sleep time calculation

[Fatos Simnica]

Dear Stata Users,

I have just started to use Stata and I am trying to calculate sleep duration (difference) between bedtime and wakeup time.
Data are in minutes after midnight. I tried different methods but what works for some does not work the others.

Bed_time	Wakeup_time
1380	360
60	480

Thank you in advance
Fatos.

[Rich Goldstein]

because you did not follow the advice in the FAQ (please read it), there is no way to be sure but I believe you have not used Stata's datetime facilities; please read

help datetime

once the times are in Stata's time format, the calculation should be easy (just subtract)

[Nick Cox]

Just this once I disagree with my friend and co-author Rich Goldstein. I see no real gain in switching to units of milliseconds. (He is right, however, if sleep extends over 3 or more days.)

The examples seem to include the two obvious possibilities: going to bed before and after midnight,

gen wanted = cond(Wakeup_time <= Bed_time, Wakeup_time - Bed_time, 1440 - Bed_time + Wakeup_time)

as 1440 = 24 * 60.

[Fatos Simnica]

Thank you very much Nick, that helped me solve the problem, but i was geting negative values so i changed it just a bit.

code;

gen sleeptime = cond ( bed_time > wakeup_time, wakeup_time + 1440 - bedtime, wakeup_time - bed_time)

[Eric de Souza]

Could you provide an example for which the use of Nick's formula was resulting in negative values?

[Nick Cox]

The first inequality should be >= (clearly, not enough sleep).

[Fatos Simnica]

Thanks again Nick!

And Eric, in the same example that i provided before.

[Eric de Souza]

Nick wrote, "not enough sleep": Probably the same here. I was mixing up true and false, and may be the order of the operators.
Fatos: as you say the examples are above.
(edited version)

[Nick Cox]

Mixing up true and false remains a big problem....