[Rd] Augment base::replace(x, list, value) to allow list= to be a predicate?

[Serguei Sokol]

Le 04/03/2023 à 01:21, Pavel Krivitsky a écrit :
> Dear All,
>
> Currently, list= in base::replace(x, list, value) has to be an index
> vector. For me, at least, the most common use case is for list= to be
> some simple property of elements of x, e.g.,
>
> x <- c(1,2,NA,3)
> replace(x, is.na(x), 0)
>
> Particularly when using R pipes, which don't allow multiple
> substitutions,
Right, but anonymous function syntax can palliate to this:

x |> (\(x) replace(x, is.na(x), 0))()


>   it would simplify many of such cases if list= could be a
> function that returns an index, e.g.,
>
> replace <- function (x, list, values, ...) {
>    # Here, list() refers to the argument, not the built-in.
>    if(is.function(list)) list <- list(x, ...)
>    x[list] <- values
>    x
> }
Before modifying the base of R, we should examine existing possibilities 
to achieve the same goal.
In this particular case and if the previous solution (anonymous 
function) is not satisfactory a thin one-line wrapper can make the job:

freplace <- function (x, list, values, ...) replace(x, 
if(is.function(list)) list <- list(x, ...) else list, values)

>
> Then, the following is possible:
>
> c(1,2,NA,3) |> replace(is.na, 0)
this becomes

c(1,2,NA,3) |> freplace(is.na, 0)

and looks quite acceptable for me.

Best,
Serguei.

>
> 			Any thoughts?
> 			Pavel
> ______________________________________________
> R-devel using r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


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Serguei Sokol
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