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Lenth, Russell V

2022-Jun-24 00:07 UTC

[Rd] [External] Re: svd() results should have a class

Bob,

I'm not talking about using svd as a generic method. I am talking about a
method FOR svd results, e.g. an S3 method like foo.svd(), for which there
already exist other methods, say foo.default and foo.qr. Currently if I wanted
to do

    svdobj <- svd(x)
    foo(svdobj)

it would not dispatch correctly because there is no svd class. Instead, it would
be handled by foo.list if it exists, and it is certainly not clear that foo.list
would do the right thing.

Russ

Sent from my iPad

On Jun 23, 2022, at 6:53 PM, Robert Harlow <rharlow86 at gmail.com> wrote:

?
Don't have a view on whether it makes sense in base R or not, but WRE
section 7.1 may be helpful to you:
https://cran.r-project.org/doc/manuals/R-exts.html#Adding-new-generics.

It's not uncommon for packages to want to make base methods generic and the
above link provides advice on how to do so.

Bob

On Thu, Jun 23, 2022 at 12:07 PM Lenth, Russell V <russell-lenth at
uiowa.edu<mailto:russell-lenth at uiowa.edu>> wrote:
Dear R-Devel,

I noticed that if we run base::svd(x), we obtain an object of class
"list". Shouldn't there be an "svd" class, in case
someone (e.g., me) wants to write methods for singular value decompositions?
Note that other matrix-decomposition routines like qr() and eigen() each return
objects having those names.

Thanks

Russ Lenth
Russell-lenth at uiowa.edu<mailto:Russell-lenth at uiowa.edu>

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Gabriel Becker

2022-Jun-24 00:18 UTC

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[Rd] [External] Re: svd() results should have a class

This does make sense to me, though I admit to not feeling super strongly
about it. Particularly in the light of the precedent from qr().

It would also be "mostly" backwards compatible, as there would not be
methods for the new class for existing code to get hung up on out of the
gate. Particularly, if class(svd(...)) was c("svd", "list")
to ensure
existing methods were always hit. I don't have a great sense of the
difference in end behavior between doing that and just having the class e
"svd", though.

Should we add this as a very late addition to the Bug BBQ list for further
discussion?

~G

On Thu, Jun 23, 2022 at 5:08 PM Lenth, Russell V <russell-lenth at
uiowa.edu>
wrote:
> Bob,
>
> I'm not talking about using svd as a generic method. I am talking about
a
> method FOR svd results, e.g. an S3 method like foo.svd(), for which there
> already exist other methods, say foo.default and foo.qr. Currently if I
> wanted to do
>
>     svdobj <- svd(x)
>     foo(svdobj)
>
> it would not dispatch correctly because there is no svd class. Instead, it
> would be handled by foo.list if it exists, and it is certainly not clear
> that foo.list would do the right thing.
>
> Russ
>
> Sent from my iPad
>
> On Jun 23, 2022, at 6:53 PM, Robert Harlow <rharlow86 at gmail.com>
wrote:
>
> ?
> Don't have a view on whether it makes sense in base R or not, but WRE
> section 7.1 may be helpful to you:
> https://cran.r-project.org/doc/manuals/R-exts.html#Adding-new-generics.
>
> It's not uncommon for packages to want to make base methods generic and
> the above link provides advice on how to do so.
>
> Bob
>
> On Thu, Jun 23, 2022 at 12:07 PM Lenth, Russell V <russell-lenth at
uiowa.edu
> <mailto:russell-lenth at uiowa.edu>> wrote:
> Dear R-Devel,
>
> I noticed that if we run base::svd(x), we obtain an object of class
> "list". Shouldn't there be an "svd" class, in case
someone (e.g., me) wants
> to write methods for singular value decompositions? Note that other
> matrix-decomposition routines like qr() and eigen() each return objects
> having those names.
>
> Thanks
>
> Russ Lenth
> Russell-lenth at uiowa.edu<mailto:Russell-lenth at uiowa.edu>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org<mailto:R-devel at r-project.org> mailing
list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
	[[alternative HTML version deleted]]

Duncan Murdoch

2022-Jun-24 00:22 UTC

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[Rd] [External] Re: svd() results should have a class

On 23/06/2022 8:07 p.m., Lenth, Russell V wrote:> Bob,
> 
> I'm not talking about using svd as a generic method. I am talking about
a method FOR svd results, e.g. an S3 method like foo.svd(), for which there
already exist other methods, say foo.default and foo.qr. Currently if I wanted
to do
> 
>      svdobj <- svd(x)
>      foo(svdobj)
> 
> it would not dispatch correctly because there is no svd class. Instead, it
would be handled by foo.list if it exists, and it is certainly not clear that
foo.list would do the right thing.
I think this would be more convincing if you gave a real example.  You 
can see the existing methods for the "qr" and "eigen"
classes using

   methods(class = "qr")
   methods(class = "eigen")

When I do it, I think I'm only seeing methods from base packages, and 
they are:

   kappa for qr
   solve for qr
   print for eigen

I think the default print method works fine for svd() results. 
kappa.svd would probably make sense, but would need some thought: 
calculating kappa on a matrix and using the help page for kappa to 
naively calculate it from the svd() of that matrix give different results:

   > set.seed(123)
   > X <- matrix(rnorm(25), 5,5)
   > kappa(X)
   [1] 90.71283
   > s <- svd(X)
   > s$d[1]/s$d[length(s$d)]
   [1] 62.68048

Duncan Murdoch
> Russ
> 
> Sent from my iPad
> 
> On Jun 23, 2022, at 6:53 PM, Robert Harlow <rharlow86 at gmail.com>
wrote:
> 
> ?
> Don't have a view on whether it makes sense in base R or not, but WRE
section 7.1 may be helpful to you:
https://cran.r-project.org/doc/manuals/R-exts.html#Adding-new-generics.
> 
> It's not uncommon for packages to want to make base methods generic and
the above link provides advice on how to do so.
> 
> Bob
> 
> On Thu, Jun 23, 2022 at 12:07 PM Lenth, Russell V <russell-lenth at
uiowa.edu<mailto:russell-lenth at uiowa.edu>> wrote:
> Dear R-Devel,
> 
> I noticed that if we run base::svd(x), we obtain an object of class
"list". Shouldn't there be an "svd" class, in case
someone (e.g., me) wants to write methods for singular value decompositions?
Note that other matrix-decomposition routines like qr() and eigen() each return
objects having those names.
> 
> Thanks
> 
> Russ Lenth
> Russell-lenth at uiowa.edu<mailto:Russell-lenth at uiowa.edu>
> 
>          [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-devel at r-project.org<mailto:R-devel at r-project.org> mailing
list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

R devel - Jun 2022 - [External] Re: svd() results should have a class

[Rd] [External] Re: svd() results should have a class

[Rd] [External] Re: svd() results should have a class

[Rd] [External] Re: svd() results should have a class