[R] Does anyone have any use for this?

[Peter Langfelder]

This would certainly simplify and make more readable some of my code where
I create multiple versions of the same plot calling the same function with
minor variations of a few of many arguments. Thanks!

Peter

On Fri, Jan 1, 2021 at 12:20 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:

> Hi all:
>
> In the course of playing around with other issues, I wrote the following
> little function that allows functions to keep state
> and easily replay and update their state.(see comments after):
>
> memify <- function(f)
> {
>    if (is.primitive(f)) {
>       cat("Cannot memify primitive functions.\n")
>       return(NULL)
>    }
>    if (!inherits(f, "function"))
>       stop("Argument must inherit from class 'function'")
>    arglist <- list()
>    structure(
>       function(...) {
>          m <- tryCatch(
>             as.list(match.call(f)[-1]),
>             error = function(e) {
>                warning("Bad function call; cannot update arguments\n")
>                return(NULL)
>             }
>          )
>          nm <- names(m)
>          hasname <- nm != "" #logical index of named values
>          if (any(hasname)) {
>             if (anyDuplicated(nm, incomparables = ""))
>                warning("Duplicated names in call; only the first will be
> used.")
>             arglist <<- modifyList(arglist, m[hasname]) ## this is what
> does the job
>          }
>          do.call(f, modifyList(m, arglist))
>       },
>       class = c("memified", class(f)))
> }
>
> Examples:
>
>  x <- 1:9; y <- runif(9)
>  plt <- memify(plot)
>  x <- 1:9; y <- runif(9)
>  plt(x,y, col = "blue")  ## plt "remembers" these arguments; i.e. keeps
> state
>  plt( type = "b") ## all other arguments as previous
>  plt(col = "red") ## ditto
>
> So my question is: Beyond allowing one to easily change/add argument values
> and replay when there are lots of arguments floating around, which we often
> use an IDE's editor to do, is there any real use for this? I confess that,
> like Pygmalion, I have been charmed by this idea, but it could well be
> useless, By all means feel free to chastise me if so.
>
> 1. I am aware that many functions already have "update" methods to "update"
> their results without re-entering all arguments -- e.g. lattice graphics,
> glm, etc.
> 2. Several packages -- rlang and R6 anyway -- but very likely more, do this
> sort of thing and way more; the price is added complexity, of course.
> 3. I realize also that keeping state would be a bad idea in many
> circumstances, e.g. essentially changing documented defaults.
>
> Reply privately to praise or bury if you do not think this is of any
> interest to readers of this list. Publicly is fine, too. If it's dumb it's
> dumb.
>
> Cheers and best wishes for a better new year for us all,
>
> Bert Gunter
>
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>
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