Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Thu Sep 21 15:51:34 CEST 2000

```Mehdi Ghafariyan <mehdi_ghafariyan at yahoo.com> writes:

> Hi all;
> I have two vectors A=c(5,2,2,3,3,2)
> and B=c(2,3,4,5,6,1,3,2,4,3,1,5,1,4,6,1,4)
> and I want to make the following matrix
> using the information I have from the above
> vectors.
>
> 	0 1 1 1 1 1
> 	1 0 1 0 0 0
> 	0 1 0 1 0 0
> 	1 0 1 0 1 0
> 	1 0 0 1 0 1
> 	1 0 0 1 0 0
>
> so the first vector says that I have 6
> elements therefor I have to make a
> 6 by 6 matrix and then I have to read
> 5 elements from the second
> vector , and put 1 in [1,j] where j=2,3,4,5,6
> and put zero elsewhere( i.e. in [1,1])
> and so on.
> Any idea how this can be done in R ?

Yep. Matrix indices:

a<-c(5,2,2,3,3,2)
b<-c(2,3,4,5,6,1,3,2,4,3,1,5,1,4,6,1,4)

n<-length(a)
M<-matrix(0,n,n)
M[cbind(rep(1:n,a),b)]<-1

--
O__  ---- Peter Dalgaard             Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
(*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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```