[R] help for bootstrap of backward stepwise logistic regression

[Frank E Harrell Jr]

Giuseppe Biondi Zoccai wrote:
> I would like to perform a bootstrap validation of a backward stepwise
> logistic regression analysis, but I am a beginner with R and I am not
> sure of how to do it.
> Is there anyone that can send me a sample file in tab format (that I
> can modify in Excel by pasting my data) and the pertinent R algorithm?
> Many thanks
> Giuseppe 
> 

You are asking for a lot and not saying that you are willing to read 
background material or help files.

To get you started, install the Design and Hmisc packages and look at 
help files for the following in Design: fastbw, lrm, validate.lrm, 
calibrate.lrm

Frank

-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University