[R] adjacency matrix

[Peter Dalgaard BSA]

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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