Jose,
You want to calculate the distance in days between a date and the date
in the previous record. See [U] 16.7 Explicit subscripting (Stata 8
User's Guide; it is [U] 13.7 in Stata 9):
clear
input year month day x1 x2
1979 8 23 0 1
1980 5 23 1 1
1980 6 6 0 0
1981 1 2 1 0
1981 2 20 1 1
end
generate date=mdy(month,day,year)
format date %d
generate nday=date - date[_n-1]
list
+-------------------------------------------------+
| year month day x1 x2 date nday |
|-------------------------------------------------|
1. | 1979 8 23 0 1 23aug1979 . |
2. | 1980 5 23 1 1 23may1980 274 |
3. | 1980 6 6 0 0 06jun1980 14 |
4. | 1981 1 2 1 0 02jan1981 210 |
5. | 1981 2 20 1 1 20feb1981 49 |
+-------------------------------------------------+
Hope this helps,
Svend
__________________________________________
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C, Denmark
Phone: +45 8942 6090
Home: +45 8693 7796
Email: [email protected]
__________________________________________
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
