This syntax is already implemented in the {purrr} package, more or
less -- you need to add a tilde before your function call for it to
work exactly as written:
purrr::map_dbl(split(mtcars, mtcars$cyl), ~ summary(lm(wt ~ mpg, .))$r.squared)
is equivalent to
sapply(split(mtcars, mtcars$cyl), function(d) summary(lm(mpg ~ wt,
d))$r.squared)
Seems like using this package is probably an easier solution for this
wish than adding a reserved variable and adding additional syntax to
the apply family as a whole.
Thanks,
-Mike
> From: Sokol Serguei <so...@insa-toulouse.fr>
> Date: Thu, Apr 16, 2020 at 12:03 PM
> Subject: Re: [Rd] suggestion: "." in [lsv]apply()
> To: William Dunlap <wdun...@tibco.com>
> Cc: r-devel <r-devel@r-project.org>
>
>
> Thanks Bill,
>
> Clearly, my first proposition for wsapply() is quick and dirty one.
> However, if "." becomes a reserved variable with this new syntax,
> wsapply() can be fixed (at least for your example and alike) as:
>
> wsapply=function(l, fun, ...) {
> .=substitute(fun)
> if (is.name(.) || is.call(.) && .[[1]]==as.name("function")) {
> sapply(l, fun, ...)
> } else {
> sapply(l, function(d) eval(., list(.=d)), ...)
> }
> }
>
> Will it do the job?
>
> Best,
> Serguei.
>
> Le 16/04/2020 à 17:07, William Dunlap a écrit :
> > Passing in a function passes not only an argument list but also an
> > environment from which to get free variables. Since your function
> > doesn't pay attention to the environment you get things like the
> > following.
> >
> > > wsapply(list(1,2:3), paste(., ":", deparse(s)))
> > [[1]]
> > [1] "1 : paste(., \":\", deparse(s))"
> >
> > [[2]]
> > [1] "2 : paste(., \":\", deparse(s))" "3 : paste(., \":\", deparse(s))"
> >
> > Bill Dunlap
> > TIBCO Software
> > wdunlap tibco.com <http://tibco.com>
> >
> >
> > On Thu, Apr 16, 2020 at 7:25 AM Sokol Serguei <so...@insa-toulouse.fr
> > <mailto:so...@insa-toulouse.fr>> wrote:
> >
> > Hi,
> >
> > I would like to make a suggestion for a small syntactic
> > modification of
> > FUN argument in the family of functions [lsv]apply(). The idea is to
> > allow one-liner expressions without typing "function(item) {...}" to
> > surround them. The argument to the anonymous function is simply
> > referred
> > as ".". Let take an example. With this new feature, the following call
> >
> > sapply(split(mtcars, mtcars$cyl), function(d) summary(lm(mpg ~ wt,
> > d))$r.squared)
> > # 4 6 8
> > #0.5086326 0.4645102 0.4229655
> >
> >
> > could be rewritten as
> >
> > sapply(split(mtcars, mtcars$cyl), summary(lm(mpg ~ wt, .))$r.squared)
> >
> > "Not a big saving in typing" you can say but multiplied by the
> > number of
> > [lsv]apply usage and a neater look, I think, the idea merits to be
> > considered.
> > To illustrate a possible implementation, I propose a wrapper
> > example for
> > sapply():
> >
> > wsapply=function(l, fun, ...) {
> > s=substitute(fun)
> > if (is.name <http://is.name>(s) || is.call(s) &&
> > s[[1]]==as.name <http://as.name>("function")) {
> > sapply(l, fun, ...) # legacy call
> > } else {
> > sapply(l, function(d) eval(s, list(.=d)), ...)
> > }
> > }
> >
> > Now, we can do:
> >
> > wsapply(split(mtcars, mtcars$cyl), summary(lm(mpg ~ wt, .))$r.squared)
> >
> > or, traditional way:
> >
> > wsapply(split(mtcars, mtcars$cyl), function(d) summary(lm(mpg ~ wt,
> > d))$r.squared)
> >
> > the both work.
> >
> > How do you feel about that?
> >
> > Best,
> > Serguei.
> >
> > ______________________________________________
> > R-devel@r-project.org <mailto:R-devel@r-project.org> mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
>
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>
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