The following snippet suggests that there is either a bug in qr(,LAPACK=T), or some
bug in my understanding. Note that the detected rank is correct (= 2) using the
default LINPACK qr, but incorrect (=3) using LAPACK. This is running on Linux Redhat
9.0, using the lapack library that comes with the Redhat distribution. I'm running R
1.7.1 compiled from the source. If the bug is in my understanding (or in the Redhat
9.0 libraries or compiler) I would much appreciate some enlightenment.
Thanks, --Mike
> X
[,1] [,2] [,3]
[1,] 1 1 1
[2,] 1 2 1
[3,] 1 3 1
[4,] 1 4 1
> qr(X)
$qr
[,1] [,2] [,3]
[1,] -2.0 -5.0000000 -2
[2,] 0.5 -2.2360680 0
[3,] 0.5 0.4472136 0
[4,] 0.5 0.8944272 0
$rank
[1] 2
$qraux
[1] 1.5 1.0 0.0
$pivot
[1] 1 2 3
attr(,"class")
[1] "qr"
> qr(X,LAPACK=T)
$qr
[,1] [,2] [,3]
[1,] -5.4772256 -1.8257419 -1.825742e+00
[2,] 0.3087742 -0.8164966 -8.164966e-01
[3,] 0.4631613 -0.3270981 -1.378276e-16
[4,] 0.6175484 -0.7892454 9.055216e-01
$rank
[1] 3
$qraux
[1] 1.182574 1.156135 1.098920
$pivot
[1] 2 1 3
attr(,"useLAPACK")
[1] TRUE
attr(,"class")
[1] "qr"
>
--
Mike Meyer, Seattle WA
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