R-beta: qr(A)$rank
Thomas Lumley
thomas at biostat.washington.edu
Tue Feb 24 22:22:56 CET 1998
On Tue, 24 Feb 1998, Bertram Zinner wrote:
> I would like to find the rank of a matrix using R. Looking through a list
> of commands it seems that the command qr should do the job. Checking a
> simple example gave me the wrong answer. Here is the example:
>
> > A <- c(1,2,3,4,5,6)
> > A <- matrix(A, nrow=2, ncol=3)
> > A
> [,1] [,2] [,3]
> [1,] 1 3 5
> [2,] 2 4 6
> > qr(A)$rank
> [1] 3
>
> The correct answer is two.
I think this is due to the mac version being so out of date. I don't have
access to it, but qr(A)$rank does work on 0.50a2 and 0.61.1 (at least
ignoring the question of whether the rank is well-defined numerically).
What does the rest of qr(A) look like? This might help in deciding what to
do, especially as a large chunk of the Mac expertise on R is temporarily
unavailable due to power failures in New Zealnd.
-thomas
Thomas Lumley
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