R help - Dec 2007 - using rcorr.cens for Goodman Kruskal gamma

Dear List,

 

I would like to calculate the Goodman-Kruskal gamma for the predicted
classes obtained from an ordinal regression model using lrm in the Design
package. I couldn't find a way to get gamma for predicted values in Design
so have found previous positings suggesting to use :

 

Rcorr.cens(x, S outx = TRUE)  in the Hmisc package

 

My question is, will this work for predicted vs observed factors?  I.e. x
predicted class and S = observed class? Or is there a better way to obtain
this? I used the maximum individual probability for each observation to
determine the predicted class. 

 

Any help appreciated, 

 

Thanks

 

Colin

 

 

 

Colin Robertson

Dept of Geography

University of Victoria

 

 


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Colin Robertson wrote:
> Dear List,
> 
>  
> 
> I would like to calculate the Goodman-Kruskal gamma for the predicted
> classes obtained from an ordinal regression model using lrm in the Design
> package. I couldn't find a way to get gamma for predicted values in
Design
> so have found previous positings suggesting to use :
> 
>  
> 
> Rcorr.cens(x, S outx = TRUE)  in the Hmisc package
> 
>  
> 
> My question is, will this work for predicted vs observed factors?  I.e. x
> predicted class and S = observed class? Or is there a better way to obtain
> this? I used the maximum individual probability for each observation to
> determine the predicted class. 
Rank correlation measures are for correlating a continuous or ordinal 
prediction with a response (continuous, ordinal, or binary).  So you 
should be able to do something like rcorr.cens(predict(fit), 
as.numeric(Y), outx=TRUE).  Note that rcorr is all lower case.  This 
assumes that the levels of Y are in order, as does lrm.

Note that the new version of lrm has a method for getting predicted mean 
scores from an ordinal lrm.

Frank
> 
>  
> 
> Any help appreciated, 
> 
>  
> 
> Thanks
> 
>  
> 
> Colin
> 
>  
> 
>  
> 
>  
> 
> Colin Robertson
> 
> Dept of Geography
> 
> University of Victoria

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