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st: Cox Calibration regression test & double graphs


From   moleps <moleps2@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Cox Calibration regression test & double graphs
Date   Tue, 9 Feb 2010 00:15:15 +0100

Dear listers,
Could someone explain or point me in the direction to a routine for doing Cox´s calibration regression test; i.e. I have the predicted probabilities for death in -p- after having fitted a logistic regression. I´ve then generated the predicted log odds by -gen logop= log(p/(1-p))-. I was then going to fit a regression line (true logodds=alpha+beta*logop) but I was unsure as to what is meant by the true log odds and how I´d calculate this.

Also Is there a trick whereby I could generate a graph with observed probability on yaxis 1 and predicted probability on the x-axis, whilst simultaneously beneath yaxis=0 and above the xaxis showing a bihistogram containing the frequencies of dead and alive patients in opposite directions. I´ve been fiddling around with yaxis 2, but I´m only able to generate a graph with bars projecting along the positive y-dimension.

Regards,

//M


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