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st: RE: Area under the curve trouble with aucdist


From   "Steichen, Thomas" <STEICHT@rjrt.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Area under the curve trouble with aucdist
Date   Tue, 24 Sep 2002 14:26:45 -0400

You might try -pkexamine-, Stata's built-in program
for such data.

Tom

> -----Original Message-----
> From: Joseph.Wagner2@med.va.gov [mailto:Joseph.Wagner2@med.va.gov] 
> Sent: Tuesday, September 24, 2002 2:05 PM
> To: statalist@hsphsun2.harvard.edu
> 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?
> *
> *   For searches and help try:
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> 
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