I tried pkexamine but got numerous error messages:
Warning: the point (0, 0) is not in your data. It will be added.
This was my program, I have 876 patients in the dataset. The only way I
could get the program to give me an AUC for each patient was to create a
little extra programming:
by id: pkexamine time conc, trapezoid
generate auc = r(auc)
sort id
qui by id: gen bign=_N
pkexamine time conc if idd1==1 & bign>2, trapezoid
generate auc = r(auc) if & bign>2
foreach var of varlist idd2-idd876{
pkexamine time conc if `var'==1 & bign>2, trapezoid
replace auc = r(auc) if `var'==1 & bign>2
}
Do I need to have -time- initialize at 0? The variable is in STATA date
format. If it needs to start at 0 I could simply subtract the value for the
first -time- from the subsequent observations for each patient. Please let
me know.
Date: Tue, 24 Sep 2002 14:26:45 -0400
From: "Steichen, Thomas" <[email protected]>
Subject: st: RE: Area under the curve trouble with aucdist
You might try -pkexamine-, Stata's built-in program
for such data.
Tom
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Sent: Tuesday, September 24, 2002 2:05 PM
> To: [email protected]
> Subject: st: Area under the curve trouble with aucdist
>
>
>
> I need to calculate the area under the curve (viral load over
> time) for
> about 1000 study participants using the trapezoidal rule. I have used
> aucdist but I am not getting a result and am not sure if I'm
> getting an
> error message.
>
> id = patient id
> time = time of viral load test
> conc = viral load value
>
> aucdist id time conc, t generate(auc)
>
> (t specifies that the integral be computed using the simple
> trapezoidal
> rule, and generate(auc) specifies to create a new variable
> with the AUC (C
> max, T max, log conc 0 -inf.))
>
> but all I'm getting is (2000) in return which is supposed to
> mean that I
> have no observations on which to perform the statistical operation.
>
> I have 9500 observations with multiple observations per
> patient, there are
> no missing data. Any suggestions as to what I may be doing wrong?
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