Thanks to Jay Kerns and Jim Lemon for their help. It's exactly what I wanted and "aggregate" is very efficient even with a huge data. Thanks

"G. Jay Kerns" <gkerns@ysu.edu> a écrit : Hi Louis,

If I am understanding your question correctly, here is one way:
suppose your matrix is M of dimension n x k.

D <- data.frame(M)  # convert to data frame
ones <- rep(1, n)   # a column of 1s

Now you can count the number of repeats of each unique row.

aggregate( ones, by = as.list(D), FUN = sum)

The output will be a data frame with the unique rows, and a column at
the end labeled "x" with the frequency of each unique row.

Once you get this you can convert to a list, manipulate, etc.  I am
sure that there exist faster/better methods.

Best,
Jay




On Dec 21, 2007 5:03 PM, Louis Martin  wrote:
> Hi,
>
> I have a matrix of duplicate rows. How to output a list the unique rows with their count? I have used "unique" to have the unique rows, but can't produce the occurences of each unique row.
>
> Thanks
>
> Louis
>
>
>
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-- 



***************************************************
G. Jay Kerns, Ph.D.
Assistant Professor / Statistics Coordinator
Department of Mathematics & Statistics
Youngstown State University
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E-mail: gkerns@ysu.edu
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