[R] Odds Ratios in rms package

[Frank Harrell]

The explanation is in the first paragraph of the help file for the
summary.rms function [inter-quartile-range odds ratios, which handles
nonlinearities].  Note that you are assuming that age has a linear effect,
which is counterintuitive.
Frank

Sebastian Pölsterl wrote
> 
> Hi,
> 
> I'm using the rms package to do regression analysis using the lrm
> function. Retrieving odds ratios is possible using summary.rms. However,
> I could not find any information on how exactly the odds ratios for
> continuous variables are calculated. It doesn't appear to be the odds
> ratio at 1 unit increase, because the output of summary.rms did not
> match the coefficient's value.
> 
> E.g. print gives me:
> 
>                 Coef    S.E.   Wald Z Pr(>|Z|)
> age              0.1166 0.0289  4.04  <0.0001
> 
> whereas summary gives me:
> 
> Factor      Low     High     Diff.   Effect S.E. Lower 0.95 Upper 0.95
> age         27.0000 37.00000 10.0000  0.78  0.20  0.40        1.17
>  Odds Ratio 27.0000 37.00000 10.0000  2.19    NA  1.49        3.22
> 
> Does anybody know how these values are obtained, especially in the
> presence of interactions?
> 
> Best regards,
> Sebastian
> 
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> 


-----
Frank Harrell
Department of Biostatistics, Vanderbilt University
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