[R] number of count of each unique row

G. Jay Kerns gkerns at ysu.edu
Sun Dec 23 00:55:06 CET 2007

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.


On Dec 21, 2007 5:03 PM, Louis Martin <louismartinbis at yahoo.fr> 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
Youngstown, OH 44555-0002 USA
Office: 1035 Cushwa Hall
Phone: (330) 941-3310 Office (voice mail)
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E-mail: gkerns at ysu.edu

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