On Oct 9, 2015, at 10:57 PM, Steven Yen wrote:
> Dear
> How do you construct a lower triangular matrix from a vector.
>
> I want to make vector
>
> a <- 1:10
>
> into a triangular matrix
>
> 1 0 0 0
> 2 3 0 0
> 4 5 6 0
> 7 8 9 10
>
I'm not sure this method with logical indexing will be the most elegant:
?lower.tri
?col
> b=matrix(0, sqrt(10)+1,sqrt(10)+1)
> b[lower.tri(b)| row(b)==col(b)] <- 1:10
> b
[,1] [,2] [,3] [,4]
[1,] 1 0 0 0
[2,] 2 5 0 0
[3,] 3 6 8 0
[4,] 4 7 9 10
> Thank you!
>
> [[alternative HTML version deleted]]
David Winsemius
Alameda, CA, USA
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