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

From: Warnes, Gregory <>
Date: Tue, 11 Sep 2012 14:02:15 +0000

On 9/7/12 2:42 PM, "peter dalgaard" <> 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

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