Nick wrote:
Svend's technique is nice, but doesn't
produce the right answer if the event
never occurs. In that case -time- is
initialised to 7, and never changed.
A fix -- which by a interesting programming law
also yields shorter code -- is to initialise
-time- as missing.
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= .
gen event=0
forvalues I = 7(-1)1 {
replace time = `I' if day`I'==1
replace event = 1 if day`I'==1
}
list
-------------------------------------------------
I don't fully agree: In the fifth observation my technique
sets time to 2 and event to 0 (censoring), Nick's sets it to
missing despite the knowledge that the subject survived
at least two days. But when all time information is missing,
the result should be missing, of course. This calls for a
slightly more, not less, complex series of commands:
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'>=.
}
recode time(0=.)
list
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]
__________________________________________
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