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st: estat phtest and factor variables (Stata 11)


From   lists@timbp.com
To   statalist@hsphsun2.harvard.edu
Subject   st: estat phtest and factor variables (Stata 11)
Date   Fri, 31 Jul 2009 23:59:49 +1000

I think this is a bug, but have I have I done something stupid?


. webuse leukemia, clear
(Leukemia Remission Study)

. stset weeks , fail(relapse )
[output omitted]
. stcox treatment1 i.wbc3cat, nolog

         failure _d:  relapse
   analysis time _t:  weeks

Cox regression -- Breslow method for ties

No. of subjects =           42                     Number of obs   =        42
No. of failures =           30
Time at risk    =          541
                                                   LR chi2(3)      =     33.02
Log likelihood  =   -77.476905                     Prob > chi2     =    0.0000

------------------------------------------------------------------------------
          _t | Haz. Ratio   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
  treatment1 |   .2834551   .1229874    -2.91   0.004     .1211042    .6634517
             |
     wbc3cat |
          2  |   3.637825   2.201306     2.13   0.033     1.111134    11.91015
          3  |   10.92214   7.088783     3.68   0.000      3.06093    38.97284
------------------------------------------------------------------------------

. estat phtest
too few variables specified
the current estimation results for cox have 4 equations so you must specify 4 new variables, or
you can use the equation() option and specify one variable at a time
r(102);

If I use the preexisting indicators wbc2 and wbc3 (as in the example in the manual) instead of the factor variable, or if I use -xi- then estat phtest works.

Tim
lists@timbp.com



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