[R] How to take the lower triangular part from a full matrix

[Romain Francois]

Le 17/06/10 06:44, ZZY ZYBOYS a écrit :
>
> Dear all:
>
> I have a question regarding on how to take the lower triangular part from a
> full matrix.
> for example
>      1 2 3                   1 0 0
>      3 4 5         to       3 4 0
>      7 8 9                   7 8 9
>
> Thanks,
> Joey

Please take at least the time to send a reproducible example on how you 
make you data, i.e:

 > x <- matrix( 1:9, nr = 3, byrow = T )


See ?lower.tri

 > x[ upper.tri(x) ] <- 0

Or see ?row and ?col

 > x[ row(x) < col(x) ] <- 0

Also note that ??triangular finds lower.tri

Romain

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Romain Francois
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