generalized matrix product ?
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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