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st: Simple programming question?
Though I seem to be too simple to figure it out.
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. Seems like it should
be simple but I'm sufficiently naive that I've not solved it. Thanks.
Brad
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Nick Cox
Sent: Tuesday, October 17, 2006 1:16 PM
To: [email protected]
Subject: st: RE: Manipulating variables with repeated observations
You should find out about -by:-.
For example:
bysort MRN (VisitDate) : gen visit = _n
by MRN : gen change = BMI[_N] - BMI[1]
Nick
[email protected]
Karen R. Fl�rez
> I have a dataset with kids BMIs that looks like this:
>
> MRN VisitDate BMI
>
> 123 10/20/04 30
>
> 123 6/11/05 25
>
> 123 4/14/06 25
>
> 222
>
> 222
>
> 222
>
>
>
> Where MRN is the unique identifier. Kids had different visits at
> different times and BMI were take at each time. How can I generate
> a variable that codes for Visit 1,2,3,etc? So that I can measure
> the change between baseline and last follow-up?
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