[R] generalized matrix product ?

[Liaw, Andy]

> From: George_Heine at blm.gov
> 
> Is there available in R a generalized inner product or matrix product,
> similar to 'outer(x,y, fun)', where one can specifiy an 
> arbitrary function
> in place of ordinary multiplication?
> 
> Here's my application.  I frequently analyze user 
> questionnaires from our
> HR/training department.  These have questions of the form
>      "please rate your skill in task X",
>  and other questions of the form
>      "Have you taken course Y?"  (or "How many years since 
> you have taken
> course Y?")
> 
> I look at rank correlation between the (suitably ordered) vectors of
> responses to a question in the first group and a question in 
> the second
> group.  (The two vectors have the same length, but I want to 
> replace the
> standard inner product with a different operation; in this case, rank
> correlation)  Repeat the process across all possible pairs of 
> questions.
> 
> Is there a way to accomplish this without nested 'for' statements?

I don't see how you can generalized inner product to get to rank
correlations.  Rank correlations are not computed by simply replacing the
multiplication in the inner product with something else, but they replace
the data values with ranks, and then compute the usual correlations on the
ranks.

If you want to generate rank correlation matrix, use cor(...,
method="spearman").

Andy

 
> Hope this is clear - thanks!
> <>=<>=<>=<>=<>=<>=<>=<>=<>=<>=<>
> George Heine, PhD
> Mathematical Analyst
> National IRM Center
> U.S. Bureau of Land Management
> voice   (303) 236-0099
> fax       (303) 236-1974
> cell      (303) 905-5382
> pager   gheine at my2way.com
> <>=<>=<>=<>=<>=<>=<>=<>=<>=<>=<>t
> 
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