Re: [Rd] Attributes of 1st argument in ...

From: Daniel Murphy <chiefmurphy_at_gmail.com>
Date: Mon, 05 Jul 2010 22:35:44 -0700

I truly am grateful for all the help.

I never would have thought defining a class union for objects that can be combined with cbind, as you do in Rmpfr. That does the trick.

Is it true that the only difference in behavior between the S4 cbind and base::cbind is that, unlike base::cbind, the S4 cbind does not seem to know the symbol of unnamed arguments? E.g.,
x<-mpfr(0:7,100)
cbind(x,x)
If so, that seems a small price to pay for the S4 functionality.

Thanks again.

Cheers,
Dan

On Mon, Jul 5, 2010 at 2:47 AM, Martin Maechler <maechler_at_stat.math.ethz.ch>wrote:

> >>>>> "DM" == Daniel Murphy <chiefmurphy@gmail.com>
> >>>>> on Sun, 4 Jul 2010 11:11:43 -0700 writes:
>
> DM> Thank you, Professor, for drawing my attention to the nifty tracemem
> DM> function. I'm using the ..1 syntax to check the properties of the S4
> class
> DM> at function call.
>
> DM> The Description at ?"cBind" tells me that I'm not alone in this
> predicament.
>
>
> DM> Just as Matrix needs its own cBind function, my package will need
> its own
> DM> cbindMondate function. Alas, subclasses of mondate will also need
> their own
> DM> binding functions, thus defeating one of the purposes of the class
> paradigm
> DM> (for binding, anyway).
>
> I don't think you see the full picture:
>
> Matrix::cBind() builds on methods::cbind2()
>
> and cbind2 / rbind2 are there (in package methods) for you to
> use setMethod() on them.
>
> BTW: When Matrix::cBind() -- and cbind2 / rbind2 in package
> methods were written,
>
> R did not have the possibility yet to write methods for "...",
> which it now does.
>
> In the package Rmpfr (arbitrary-precision number ["mpfr"] computing),
> where I also define methods for matrices of such "mpfr" numbers
> (classes "mpfrMatrix" and "mpfrArray"),
> I use the new feature of defining methods for "..." :
>
> setGeneric("cbind", signature = "...")
>
> setMethod("cbind", "Mnumber",
> function(..., deparse.level = 1) {
> args <- list(...)
> if(all(sapply(args, is.atomic)))
> return( base::cbind(..., deparse.level = deparse.level) )
> ## else: at least one is "mpfr(Matrix/Array)"
>
> if(any(sapply(args, is.character))) {
> ## result will be <character> matrix !
> isM <- sapply(args, is, class2 = "mpfr")
> args[isM] <- lapply(args[isM], as, Class = "character")
> return(do.call(base::cbind,
> c(args,
> list(deparse.level=deparse.level))))
>
> } else if(any(sapply(args, is.complex))) {
> ## result will be <complex> matrix;
> ## in the future <complex_mpfr> ???
>
> stop("cbind(...) of 'complex' and 'mpfr' objects is not
> implemented")
> ## give at least warning !!
> }
> ## else
>
> ..........
> ..........
> })
>
>
> where I use a useful class union
>
> setClassUnion("Mnumber",
> members = c("array_or_vector", # *but* must be numeric-like
> "mpfr", "mpfrArray", "mpfrMatrix"))
>
> ----
>
> As always, I'd recommend to read the R source, rather than just
> investigate the installed package.
> You can get the *source* tarbal, i.e., the *.tar.gz file from
> CRAN, or, as it's all on R-forge,
> http://rmpfr.r-forge.r-project.org/
> you can get the source tarball here,
> https://r-forge.r-project.org/R/?group_id=386
> or browse the source at
> https://r-forge.r-project.org/scm/viewvc.php/pkg/?root=rmpfr
>
> But if I were you I'd get it via
> svn checkout svn://svn.r-forge.r-project.org/svnroot/rmpfr/pkg Rmpfr
>
>
>
> DM> As an aside, I wonder why, on around line 75, cBind uses 'rep.int
> ("",
> DM> ncol(r))' rather than the slightly faster 'character(ncol(r))'.
>
> Well, I would not remember, but the first one is a more self-explaining,
> ... and I would guess strongly that time difference is
> irrelevant in the context where it's used...
> ... but then thanks for your hint :-)
>
> Martin
>
> <snip>

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