[R] unique columns in a matrix and number of each

[Gabor Grothendieck]

Define inner as in:
http://tolstoy.newcastle.edu.au/R/e4/help/08/08/19562.html
and use that with identical to define an inner product:

m <- matrix(c(1, 2, 1,  2, 3, 2), 2) # test matrix
m
colSums(inner(m, u <- unique(m,,2), identical))
u

Please provide actual code to create test examples and expected results
when you post. Read the last line to every message in r-help and the
posting guide.


On Sat, Nov 22, 2008 at 3:42 PM, Salas, Andria Kay <aks2515 at uncw.edu> wrote:
> I need help determining the unique columns of a matrix and the numbers of each unique column.  For example, let's say I have a matrix with 6 columns, 2 of these are filled with the value of 1 and the other 4 are filled with the value of 0.  I would then like to have a command that tells me what the unique columns are (so columns with 1s and columns with 0s) and the number of each type of column (so 2 columns of 1s and 4 columns of 0s) that occur in the matrix.
>
> Thank you for any help anyone can provide!!  I have been very impressed with the help that I have received so far!!  Thank you!
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