[R-pkg-devel] Recommendation on qr method export

[Charles Determan]

Thanks for the input Peter.  I suppose I never looked at lm() to see how it
was used there.  Given that though, do you see any reason then to not
create an S3/S4 method if different methods are used for different
functions?  I'm just looking for some design guidance from the community
here before I just implement something that may cause more confusion.

Regards,
Charles

On Tue, Aug 2, 2016 at 4:34 PM, Peter Dalgaard <pdalgd at gmail.com> wrote:

> Not strictly what you're asking, but at some point it may be important to
> note that the "QR" method used by lm() and friends (notably anova() and
> aov()) actually relies on successive orthogonalization. This does yield a
> QR decomposition but the reverse is not true. A generic X=QR decomposition
> does orthogonalize, but it does not necessarily hold that the first k
> columns of Q spans the same subspace as the first k columns of X. LINPACK's
> QR happens to be implemented as successive orthogonalization, but LAPACK's
> is not, so only the former is usable with lm().
>
> So, I suppose what I am getting at is that not even lm() uses qr(), it
> calls LINPACK directly.
>
> -pd
>
>
> > On 02 Aug 2016, at 21:17 , Charles Determan <cdetermanjr at gmail.com>
> wrote:
> >
> > Hello,
> >
> > I am currently working on an implementation of QR decomposition
> (leveraging
> > a C++ library via Rcpp).  Naturally I would like to have the R syntax as
> > similar as possible to base R 'qr' function.  Given the class structure
> of
> > my package my instinct was to export an S4/S3 method.
> >
> > However, the QR decomposition doesn't store the final QR matrix in the
> same
> > format as base R via LINPACK, nor does it return 'qraux', 'rank' or
> 'pivot'
> > objects but instead a 'betas' object.  The final 'R' and 'Q' matrices are
> > in fact identical to those ultimately returned by qr.R or qr.Q.
> >
> > So my question is, given these differences, should I just create a
> > different function name or would creating a qr.myclass dispatch be
> > acceptable (whether S3 or S4)?  I would prefer the latter as I would like
> > the classes to potentially take advantage of previously written code
> using
> > 'qr'.
> >
> > Thanks,
> > Charles
> >
> >       [[alternative HTML version deleted]]
> >
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>
>

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