[R] lambda, uncertainty coefficient (& Somers D)

Frank E Harrell Jr f.harrell at vanderbilt.edu
Tue Apr 18 16:11:42 CEST 2006

Antti Arppe wrote:
> Dear colleagues in R,
> Has anybody implemented the
> 1) (Goodman & Kruskal) lambda
> or the
> 2) (Thiel's) uncertainty coefficient
> statistics (in the asymmetric and symmetric forms), or is anyone aware 
> that they might reside in some package? A search in the R archives 
> does indicate that they are (somehow) part of the CoCo package, but I 
> would rather not start learning how to transform my data into 
> CoCo-format in order to access these functions, regardless of whether 
> the CoCo versions are actually intended for calculating the actual 
> statistic or for some other package internal purposes, as may 
> sometimes be the case.
> Furthermore, it appears to me that the 'somers2' function in the Hmisc 
> package applies Somers' D only to 2x2 and not larger tables. Am I 
> mistaken, or does there exist somewhere else an implementation of the 
> Somers' D statistic for the more general RxC tables? This was queried 
> in 1999, but no response seemed then to be forthcoming.

Somers' D is for a 2-category response variable.  X may have any number 
of categories as long as they are ordered.

Frank Harrell

> Thanks and regards,
>  	-Antti Arppe

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

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