Enzo,
Thanks for the suggestion. Your code works perfectly on the data
provided, but unfortunately occupational studies often include follow-up
without an increase in cumulative does. When xin=xout using stsplit with
x as the time scale does not work, because records with xin=xout are
rejected. I should have included this in my test data.
I bodged the code by adding 0.00001 to xout when xin=xout, and then
removing it later, but it adds up to rather a messy solution,
particularly when xout corresponds to one of the break points for
ecxposure group.
But at least its a start, and I ma grateful for your help,
Michael
On Fri, 2004-04-23 at 14:17, Enzo Coviello wrote:
> At 12.33 22/04/04 +0100, you wrote:
> >Using stlexis (stata 5) I used to be able to split follow-up time
> >according to cumulative dose (x) of some exposure.
> >
> >For example, I could convert these three records
> >
> > id timein timeout xin xout fail
> >-------------------------------------------
> > 1 0 5 0 40 0
> > 1 5 10 40 180 0
> > 1 10 15 180 220 1
> >
> >into these five records
> >
> > id timein timeout fail exp_grp
> > 1 0.000 5.000 0 0-100
> > 1 5.000 7.143 0 0-100
> > 1 7.143 10.000 0 100-200
> > 1 10.000 12.500 0 100-200
> > 1 12.500 15.000 1 200-300
> >
> >making the assumption of a linear increase in cumulative dose between
> >readings.
> >
> >Somewhere along the line the contributed command stlexis was replaced by
> >the official command stsplit, but I can't figure out how to do this with
> >stsplit. Even worse, I can't figure out how to do it at all without going
> >back to stlexis.
>
>
> Dear prof Hills,
>
> maybe this could an empirical solution:
>
> . gen xoutcopy=xout
>
> . stset xout,enter(xin) id(id) f(fail)
>
>
> . stsplit exposure, at(100 200)
> (2 observations (episodes) created)
>
> . bysort id (xout) : replace timeout = timein+ (timeout-timein) * (_t-_t0)
> / (xoutcopy-_t0)
>
> . bysort id (_t) : replace timein=timeout[_n-1] if _n>1
>
> . stset timeout,enter(timein) id(id) f(fail)
>
> . list id timein timeout xin xout exposure
>
> +------------------------------------------------+
> | id timein timeout xin xout exposure |
> |------------------------------------------------|
> 1. | 1 0 5 0 40 0 |
> 2. | 1 5 7.14286 40 100 0 |
> 3. | 1 7.14286 10 40 180 100 |
> 4. | 1 10 12.5 180 200 100 |
> 5. | 1 12.5 15 180 220 200 |
> +------------------------------------------------+
>
>
> Enzo
>
>
>
> ^^^^^^^^^^^^^^^^
> Enzo Coviello
> Dipartimento di Prevenzione ASL BA/1
> via L. Barbera 27 - 70055 MINERVINO MURGE (BA)
> Italy
> tel - fax +39 0883 691053
> tel (home) +39 0883 695055
>
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>
>
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