[R] How to define new matrix based on an elementary row oper

[(Ted Harding)]

On 28-Aug-10 13:15:47, Cuckovic Paik wrote:
> Thank all help help. Ted's intuitive single step definition
> is what I want. 
> I try to teach elementary Linear Algebra using R to manupilate
> matrices.
> Since my students have no programming experience at all, any fancy and
> muliple step definition in matrix row operation will confuse them.
> Again, I appreciate the suggestions from all of you! 
> --

Just to avoid any misunderstanding: My contribution was an explanatory
comment to Gabor's solution. It was Gabor who gave the solution!

But, while I am at it, if you are teaching elementary Linear Algebra
and matrix manipulation, note that the desired result (rows 1, 2 & 4
of A, with row 3 = 2*(row 1 of A) + (row 3 of A)) can be obtained
using a matrix product:

1  0  0  0  %*%   1  5  9 13
0  1  0  0        2  6 10 14
2  0  1  0        3  7 11 15
0  0  0  1        4  8 12 16

i.e. (in R):

  (diag(nrow(A)) + c(0,0,2,0, 0,0,0,0, 0,0,0,0, 0,0,0,0))%*%A
  #      [,1] [,2] [,3] [,4]
  # [1,]    1    5    9   13
  # [2,]    2    6   10   14
  # [3,]    5   17   29   41
  # [4,]    4    8   12   16

(as before).
Ted.

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Date: 28-Aug-10                                       Time: 15:12:03
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