From: Berend Hasselman <bhh_at_xs4all.nl>

Date: Wed, 11 Jun 2008 07:39:38 -0700 (PDT)

Date: Wed, 11 Jun 2008 07:39:38 -0700 (PDT)

stefan.petersson wrote:

*>
**>
**> ng,
**>
*

> I have a matrix (x) with binary content. Each row of the matrix holds

*> exactly one 1, and the rest of the row is zeros. The thing is that I need
**> to 'collapse' the matrix to one column where each row holds the original
**> column index of the 1's (y). Sometimes, the matrix is quite large, so I
**> have a perfomance problem.
**>
**> x <- matrix(c(1,0,0, 0,0,1, 0,1,0, 0,0,1, 0,1,0, 1,0,0),ncol=3,byrow=T)
**> x
**> [,1] [,2] [,3]
**> [1,] 1 0 0
**> [2,] 0 0 1
**> [3,] 0 1 0
**> [4,] 0 0 1
**> [5,] 0 1 0
**> [6,] 1 0 0
**>
**> In the matrix above, on the first row, the 1 is in column 1, hence '1' on
**> the first row in the matrix below. On the second row in the matrix above,
**> the 1 is in column 3, hence the '3' on the second row in the matrix below.
**> And so on...
**>
**> y
**> [,1]
**> [1,] 1
**> [2,] 3
**> [3,] 2
**> [4,] 3
**> [5,] 2
**> [6,] 1
**>
**>
*

max.col(x)

-- View this message in context: http://www.nabble.com/Matrix-transformation-problem-tp17773270p17779431.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Wed 11 Jun 2008 - 15:07:10 GMT

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