R help - Mar 2011 - Matrix building to remove for loops

Hello R users,

I would like to reduce the number of for loops in my code. I build these
matrices (50000 times). The main diagonal are 1s and the two sides along the
main diagonal mirror each other as follows:


i<-5
fi<-matrix(0,nrow=i,ncol=i)#floral inhibition matrix for(r in 1:i){ for(c in
1:i){ if(r==c){ fi[r,c]<-1 }else if(r<c){ fi[r,c]<-1-runif(1)^.5 }else{
fi[r,c]<-fi[c,r] } } }
fi

Any thoughts?

Sincerely,
Brian

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Try this:

fi_2 <- diag(1, i)
fi_2[lower.tri(fi_2)] <- 1 - runif(sum(lower.tri(fi_2))) ^ .5
fi_2[upper.tri(fi_2)] <- fi_2[lower.tri(fi_2)]

On Tue, Mar 15, 2011 at 7:51 PM, Brian Pellerin <
brianpatrickpellerin@gmail.com> wrote:
> Hello R users,
>
> I would like to reduce the number of for loops in my code. I build these
> matrices (50000 times). The main diagonal are 1s and the two sides along
> the
> main diagonal mirror each other as follows:
>
>
> i<-5
> fi<-matrix(0,nrow=i,ncol=i)#floral inhibition matrix for(r in 1:i){
for(c
> in
> 1:i){ if(r==c){ fi[r,c]<-1 }else if(r<c){ fi[r,c]<-1-runif(1)^.5
}else{
> fi[r,c]<-fi[c,r] } } }
> fi
>
> Any thoughts?
>
> Sincerely,
> Brian
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
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>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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