[R] Efficent way to create an nxn upper triangular matrix of one's

[Christos Hatzis]

Here is a way to do this:

round(upper.tri(matrix(1, 9, 9)))

Or if you also need the diagonal of one's

round(upper.tri(matrix(1, 9, 9), diag = TRUE))

-Christos 
 
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Dale Steele
> Sent: Wednesday, February 11, 2009 4:23 PM
> To: R help
> Subject: [R] Efficent way to create an nxn upper triangular 
> matrix of one's
> 
> The code below create an nxn upper triangular matrix of 
> one's.  I'm stuck on finding a more efficient vectorized way 
> - Thanks.  --Dale
> 
> n <- 9
> data <- matrix(data=NA, nrow=n, ncol=n)
> data
> for (i in 1:n) {
>     data[,i] <- c(rep(1,i), rep(0,n-i))
> }
> data
> 
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