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

Bert Gunter gunter.berton at gene.com
Tue May 8 23:34:29 CEST 2007

```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.
--------------------------------------------------------

This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}

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