[Rd] Suggest adding a 'pivot' argument to qr.R

Warnes, Gregory gregory.warnes at novartis.com
Tue Sep 11 16:02:15 CEST 2012

On 9/7/12 2:42 PM, "peter dalgaard" <pdalgd at gmail.com> wrote:

>On Sep 7, 2012, at 17:16 , Tim Hesterberg wrote:
>> I suggest adding a 'pivot' argument to qr.R, to obtain columns in the
>> same order as the original x, so that
>>  a <- qr(x)
>>  qr.Q(a) %*% qr.R(a, pivot=TRUE)
>> returns x.
>That would come spiraling down in flames the first time someone tried to
>use backsolve on it, wouldn't it? I mean, a major point of QR is that R
>is triangular; doesn't make much sense to permute the columns without
>retaining the pivoting permutation.

As I understand Tim's proposal, the pivot argument defaults to FALSE, so
the new behavior would only be activated at the user's request.


Gregory Warnes, Ph.D.
Sr. Expert Modeler
Modeling and Simulation
CA Phone: +1 617 871-8498
gregory.warnes at novartis.com

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