[R] assign a constant to a different column for each row

[M.Kondrin]

uaca at alumni.uv.es wrote:
> Hi all
> 
> I want to assign a constant to a different column for each row
> 
> eg:
> 
> m[1,2] <- 0;
> m[2,3] <- 0;
> m[3,1] <- 0;
> m[4,2] <- 0;
> m[5,1] <- 0;
> ...
> 
> etc...
>           
> i've tried apply/tapply with no luck
> 
> and also the following
> 
> coefs <- rtt.abs[,5:8];
> coefs.i <- coefs[] == 1;
> coefs[coefs.i] <- 0;
> 
> wich results in
> 
> "matrix subscripts not allowed in replacement" 
> 
> error message, for wich I have not found any workaround
> 
> a trivial for() loop is not fast enough
> 
> any help would be greatly appreciated, (maybe a gun too) I'm disperated :-\
> 
> Thanks in advance
> 
> 	Ulisses
> 
> 
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> 
 > cbind(c(1,2,3),c(4,5,6),c(6,7,8))->l
 > l
      [,1] [,2] [,3]
[1,]    1    4    6
[2,]    2    5    7
[3,]    3    6    8
 > l[1:2,1:3]<-4
 > l
      [,1] [,2] [,3]
[1,]    4    4    4
[2,]    4    4    4
[3,]    3    6    8
 >