[R] Looking for a cleaner way to implement a setting certainindices of a matrix to 1 function

[Leeds, Mark (IED)]

That's a good idea : I didn't realize that my matrices would look so bad
in the final email. All I want
To do is output 1's in the diagonal elements and zero's everywhere else
but the matrix is not square so by diagonals I
Really mean if

Lagnum = 1 then the elements are (1,1), (2,2), (3,3),(4,4),(5,5),(6,6)

Lagnum = 2 then the elements (1,1), (2,2),
(3,3),(4,4),(5,5),(6,6),(7,1),(8,2),(9,3),(10,4),(11,5),(12,6)

Lagnum = 3 then the elements (1,1), (2,2),
(3,3),(4,4),(5,5),(6,6),(7,1),(8,2),(9,3),(10,4),(11,5),(12,6),(13,1),(1
4,2),(15,3),(16,4),(17,5),
(18,6)

And lagnum always has to be greater than or equal to 1 and less than or
equal to (number of cols/number of rows ). Thanks
For your advice.


-----Original Message-----
From: Bert Gunter [mailto:gunter.berton at gene.com] 
Sent: Tuesday, May 08, 2007 5:34 PM
To: Leeds, Mark (IED); r-help at stat.math.ethz.ch
Subject: RE: [R] Looking for a cleaner way to implement a setting
certainindices of a matrix to 1 function

Suggestion:

You might make it easier for folks to help if you explained in clear and
simple terms what you are trying to do. Code is hard to deconstruct.


Bert Gunter
Genentech Nonclinical Statistics


-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Leeds, Mark (IED)
Sent: Tuesday, May 08, 2007 2:22 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Looking for a cleaner way to implement a setting
certainindices of a matrix to 1 function

I wrote an ugly algorithm to set certain elements of a matrix to 1
without looping and below works and you can see what The output is below
the code.

K<-6
lagnum<-2

restrictmat<-matrix(0,nrow=K,ncol=K*3)
restrictmat[((col(restrictmat) - row(restrictmat) >= 0 ) &
(col(restrictmat)-row(restrictmat)) %% K == 0)]<-1
restrictmat[,(lagnum*K+1):ncol(restrictmat)]<-0

 restrictmat
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[,13] [,14] [,15] [,16] [,17] [,18]
[1,]    1    0    0    0    0    0    1    0    0     0     0     0
0     0     0     0     0     0
[2,]    0    1    0    0    0    0    0    1    0     0     0     0
0     0     0     0     0     0
[3,]    0    0    1    0    0    0    0    0    1     0     0     0
0     0     0     0     0     0
[4,]    0    0    0    1    0    0    0    0    0     1     0     0
0     0     0     0     0     0
[5,]    0    0    0    0    1    0    0    0    0     0     1     0
0     0     0     0     0     0
[6,]    0    0    0    0    0    1    0    0    0     0     0     1
0     0     0     0     0     0

For lagnum equals 1 , it also works :

 restrictmat
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[,13] [,14] [,15] [,16] [,17] [,18]
[1,]    1    0    0    0    0    0    0    0    0     0     0     0
0     0     0     0     0     0
[2,]    0    1    0    0    0    0    0    0    0     0     0     0
0     0     0     0     0     0
[3,]    0    0    1    0    0    0    0    0    0     0     0     0
0     0     0     0     0     0
[4,]    0    0    0    1    0    0    0    0    0     0     0     0
0     0     0     0     0     0
[5,]    0    0    0    0    1    0    0    0    0     0     0     0
0     0     0     0     0     0
[6,]    0    0    0    0    0    1    0    0    0     0     0     0
0     0     0     0     0     0

But I am thinking that there has to be a better way particularly because
I'll get an error if I set lagnum to 3. 
Any improvements or total revampings are appreciated. The number of
columns will always be a multiple of the number of rows So K doesn't
have to be 6. that was just to show what the commands do.
thanks.
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