[R] Matrix Construction; Subdiagonal

[Sundar Dorai-Raj]

You can always write your own function:

myDiag <- function(x, vec, k) {
  x[row(x) == col(x) - k] <- vec
  x
}

myDiag(A, vec, -1)

Of course, you should probably do some input checking too.

--sundar

On Wed, Mar 11, 2009 at 4:57 PM, Stu Field <sgf at colostate.edu> wrote:
> Sure, that'll work fine, thanks.
> But I guess I was looking for something more similar to MatLab, I'm really
> surprised R doesn't have a preset command for this (?)
> Thanks again,
> Stu
> On 11 • Mar • 2009, at 5:49 PM, Sundar Dorai-Raj wrote:
>
> Does this help?
>
> A <- matrix(0, 6, 6)
> vec <- 1:5
> A[row(A) == col(A) + 1] <- vec
>
> --sundar
>
> On Wed, Mar 11, 2009 at 4:42 PM, Stu Field <sgf at colostate.edu> wrote:
>
> I'm trying to enter a vector into the subdiagonal of a matrix but
>
> cannot find a command in R which corresponds to the MatLab version of
>
> diag(vec, k), where vec = the vector of interest, and k = the diagonal
>
> (k=0 for the diagonal; k=-1 for the subdiagonal; k=1 for
>
> superdiagonal, etc.)
>
> Is there an equivalent command in R?
>
> I'm looking for something like this:
>
> vec = seq(1, 5, 1)        # vector of interest
>
> A = xyz(vec,-1)           # creates a 6x6 matrix with vec on the
>
> subdiagonal
>
> where xyz is some function similar to diag, but with differing
>
> arguments.
>
> I can't believe there is not a simple way to do this...
>
> Thanks for your help,
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Stu Field, PhD
>
> Postdoctoral Fellow
>
> Department of Biology
>
> Colorado State University
>
> 1878 Campus Delivery
>
> Fort Collins, CO 80523-1878
>
> Office: E208 Anatomy/Zoology
>
> Phone: (970) 491-5744
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>
>
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> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Stu Field, PhD
> Postdoctoral Fellow
> Department of Biology
> Colorado State University
> 1878 Campus Delivery
> Fort Collins, CO 80523-1878
> Office: E208 Anatomy/Zoology
> Phone: (970) 491-5744
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>