On Aug 27, 2010, at 9:21 PM, Cuckovic Paik wrote:
I'm not absolutely sure I know what you mean by elementary row
operations ... you are supposed to offer test cases and specify the
desired output on r-help to support the aging faculties of the helpeRs
in this case ... having only the vaguest of memories of my linear
algebra lessons from the late 60's, but will exemplify: A) addition
of a factor times another row and b) exchanges of rows:
> tst<-matrix(1:16, 4,4)
> tst
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 2 6 10 14
[3,] 3 7 11 15
[4,] 4 8 12 16
> tst2 <- tst
# note that I kept tst in reserve, so to speak.
> tst2[2, ] <- tst2[2, ] + 3*tst2[4, ] #add 3 times row 4 to row 2
> tst2
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 14 30 46 62
[3,] 3 7 11 15
[4,] 4 8 12 16
> tst2 <- tst #restore to its original state
> tst2 <- tst2[c(1,4,3,2), ] #transpose rows
> tst2
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 4 8 12 16
[3,] 3 7 11 15
[4,] 2 6 10 14
--
David Winsemius, MD
West Hartford, CT
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