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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [[alternative HTML version deleted]]
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 > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > ? ? ? ?[[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >
Why should there be a simple way? R is not primarily a matrix language.
Perhaps this will help:
xyz <- function (v, k) {
n <- length(v) + abs(k)
x <- matrix(0, n, n)
if (k == 0)
diag(x) <- v
else if (k < 0)
{ ## sub-diagonal
j <- 1:(n+k)
i <- (1 - k):n
x[cbind(i, j)] <- v
} else
{ ## super-diagonal
i <- 1:(n-k)
k <- (1 + k):n
x[cbind(i, j)] <- v
}
x
}
modify, extend, simplify, ... as you wish.
Bill Venables.
Bill Venables
http://www.cmis.csiro.au/bill.venables/
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Stu Field
Sent: Thursday, 12 March 2009 9:43 AM
To: r-help at r-project.org
Subject: [R] Matrix Construction; Subdiagonal
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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[[alternative HTML version deleted]]
______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
On Wed, Mar 11, 2009 at 11:49 PM, Sundar Dorai-Raj <sdorairaj at gmail.com> wrote:> Does this help? > > A <- matrix(0, 6, 6) > vec <- 1:5 > A[row(A) == col(A) + 1] <- vecMaybe, more simply: A <- matrix(0, 6, 6) vec <- 1:5 diag(A[-1,]) <- vec Paul