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Re: st: AUC above a fixed value


From   Svend Juul <SJ@SOCI.AU.DK>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: AUC above a fixed value
Date   Tue, 26 Aug 2008 19:40:13 +0200

Alvine Bissery wrote:
 
I need to calculate a AUC of "hem"  with  8 time measurements
 
time hem
0 116
1 97
2 101
3 114
6 125
12 121
18 118
24 128
 
But I need only AUC above the threshold of hem=110
 
Ronan Conroy gave the solution, but:
 
... my problem is to create the new time variable, because time
values 1 and 2 have changed.
 
I need a new time variable (time_101) 
time_110    hem_101
   0       6
  x1       0
  x2       0
   3       4
   6       15
   12      11
   18      8
   24      18
 
Where x1 is between 0 and 1 , and  1<x2<3
 
=====================================================
 
It is not clear to me why a new time variable is needed, but:
 
    . generate time_110 = time
    . replace time_110 = (time + time[_n+1])/2 if hem<110
    . generate hem_110 = (hem-110)*(hem>110)

    . list , clean
           time   hem   time_110   hem_110  
      1.      0   116          0         6  
      2.      1    97        1.5         0  
      3.      2   101        2.5         0  
      4.      3   114          3         4  
      5.      6   125          6        15  
      6.     12   121         12        11  
      7.     18   118         18         8  
      8.     24   128         24        18  
 
Hope this helps
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, work:   +45 8942 6090 
Phone, home:   +45 8693 7796 
Fax:           +45 8613 1580 
E-mail:        sj@soci.au.dk 
_________________________________________________________ 

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