Brad wrote:
I have data like the following:
id day1 day2 day3 day4 day5 day6 ... day90
1 0 0 0 1 0 0 ... 0
2 0 0 0 0 1 1 ... .
3 1 1 1 1 1 1 ... 1
4 0 0 0 0 0 0 ... 0
Assume that a 1 on day`i' represents failure. I'm trying to generate a
variable that gives days to failure for survival analysis. E.g., subject 1
failed on day 4, subject 5 failed on day 5, subject 3 failed on day 1,
subject 4 did not fail and would be considered censored. 90 days worth of
data were collected but not all subjects were observed for the full 90-day
period. Also note that subjects may be recorded as failing (drinking at
hazardous levels) on any combination of days during the 90-day period. I'm
trying to calculate number of days to first failure....
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In the following example I use only 7 days, but the principle is the same. To find the first day of changed status, examine days in reverse order:
clear
input id day1 day2 day3 day4 day5 day6 day7
1 0 0 0 1 0 0 0
2 0 0 0 0 1 1 .
3 1 1 1 1 1 1 1
4 0 0 0 0 0 0 0
5 0 0 . . . . .
end
gen time=7
gen event=0
forvalues I = 7(-1)1 {
replace time = `I' if day`I'==1
replace event = 1 if day`I'==1
replace time = `I'-1 if day`I'>=.
}
list
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, work: +45 8942 6090
Phone, home: +45 8693 7796
Fax: +45 8613 1580
E-mail: [email protected]
_________________________________________________________
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