R help - Feb 2012 - Discrimination and calibration of Cox model

I have been working on fitting Cox model for prediction by using rms package.
I want to measure model's calibartion and discrimination. Discrimination was
measured by using validate() in rms, Dxy can be transferred to Harrell's c
index. But in this way, I cannot get 95%CI of c index. How can I do this in
R? And by the way, what value should be in c index to present the model's
well?

Calibration was using calibrate() in rms, but I cannot get the calibration
plot which presented the concorance of predicted and observed events in Cox
model. How can I do this calibration plot of Cox model in R. 



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On Feb 7, 2012, at 11:07 PM, cmh wrote:
> I have been working on fitting Cox model for prediction by using rms  
> package.
> I want to measure model's calibartion and discrimination.  
> Discrimination was
> measured by using validate() in rms, Dxy can be transferred to  
> Harrell's c
> index. But in this way, I cannot get 95%CI of c index. How can I do  
> this in
> R? And by the way, what value should be in c index to present the  
> model's
> well?
Harrell has answered this question several times on this list. It  
shouldn't be that difficult to search them out.
>
> Calibration was using calibrate() in rms, but I cannot get the  
> calibration
> plot which presented the concorance of predicted and observed events  
> in Cox
> model. How can I do this calibration plot of Cox model in R.
>
There _are_ worked examples on the help pages.
>
>
> --

David Winsemius, MD
West Hartford, CT