generating time duration from strings

[Andrea Ciaccio]

Hi Everyone,
I am using Italian Time use data. Since I have the time at which an episode begins and the time at which the episode ends, is there a way to tell STATA that those strings are duration (i.e. is there a way to generate the duration of an episode once having the time at which you start doing that activity and the time at which you end doing it) ?
Since my data are confidential I will post an example of my dataset:

input str2(starthour startminute endhour endminute)
"04" "00" "09" "50"
"09" "50" "10" "00"
"10" "00" "10" "10"
"10" "10" "11" "30"
"11" "30" "12" "50"
"12" "50" "15" "00"
"15" "00" "16" "00"
"16" "00" "16" "50"
"16 "50" "17" "50"
"17" "50" "18" "00"
"18" "00" "18" "30"
"18" "30" "18" "50"
"18" "50" "21" "00"
"21" "00" "21" "30"
"21" "30" "22" "00"
"22" "00" "22" "40"
"22" "40" "04" "00"

where "starthour" is the hour at which you start doing a given activity, "startminute" is the minute in which you start a given activity, "endhour" and "endmin" is the time at which you end doing that activity!
Thank you all in advance,
Andrea

[William Lisowski]

Perhaps this sample code will start you in a useful direction. And thank you for including sample data that spanned two days - that's always something that needs to be considered.

clear
input str2(starthour startminute endhour endminute)
"04" "00" "09" "50"
"09" "50" "10" "00"
"10" "00" "10" "10"
"10" "10" "11" "30"
"11" "30" "12" "50"
"12" "50" "15" "00"
"15" "00" "16" "00"
"16" "00" "16" "50"
"16" "50" "17" "50"
"17" "50" "18" "00"
"18" "00" "18" "30"
"18" "30" "18" "50"
"18" "50" "21" "00"
"21" "00" "21" "30"
"21" "30" "22" "00"
"22" "00" "22" "40"
"22" "40" "04" "00"
end
destring starthour startminute endhour endminute, replace
format starthour startminute endhour endminute %02.0f
replace endhour = endhour+24 if endhour < starthour 
generate long min_dur = (endhour-starthour)*60 + (endminute-startminute)

. list, noobs sepby(starthour)

  +----------------------------------------------------+
  | starth~r   startm~e   endhour   endmin~e   min_dur |
  |----------------------------------------------------|
  |       04         00        09         50       350 |
  |----------------------------------------------------|
  |       09         50        10         00        10 |
  |----------------------------------------------------|
  |       10         00        10         10        10 |
  |       10         10        11         30        80 |
  |----------------------------------------------------|
  |       11         30        12         50        80 |
  |----------------------------------------------------|
  |       12         50        15         00       130 |
  |----------------------------------------------------|
  |       15         00        16         00        60 |
  |----------------------------------------------------|
  |       16         00        16         50        50 |
  |       16         50        17         50        60 |
  |----------------------------------------------------|
  |       17         50        18         00        10 |
  |----------------------------------------------------|
  |       18         00        18         30        30 |
  |       18         30        18         50        20 |
  |       18         50        21         00       130 |
  |----------------------------------------------------|
  |       21         00        21         30        30 |
  |       21         30        22         00        30 |
  |----------------------------------------------------|
  |       22         00        22         40        40 |
  |       22         40        28         00       320 |
  +----------------------------------------------------+