[R] Change Function based on ifelse() condtion

[Christofer Bogaso]

Below is my full implementation (tried to make it simple as for demonstration)

Lapply_me = function(X = X, FUN = FUN, Apply_MC = FALSE, ...) {
if (Apply_MC) {
return(mclapply(X, FUN, ...))
} else {
if (any(names(list(...)) == 'mc.cores')) {
myList = list(...)[!names(list(...)) %in% 'mc.cores']
}
return(lapply(X, FUN, myList))
}
}


Lapply_me(as.list(1:4), function(xx) {
if (xx == 1) return('a')
if (xx == 2) return('b')
if (xx == 3) return('c')
if (xx == 4) return('d')
}, Apply_MC = FALSE, mc.cores = 2)

Error message :

Error in FUN(X[[i]], ...) : unused argument (list())

Kindly note that, with Apply_MC = TRUE, it is working perfectly.

On Sun, Mar 4, 2018 at 10:45 PM, Eric Berger <ericjberger at gmail.com> wrote:
> That's fine. The issue is how you called Lapply_me(). What did you pass as
> the argument to FUN?
> And if you did not pass anything that how is FUN declared?
> You have not shown that in your email.
>
>
>
>
> On Sun, Mar 4, 2018 at 7:11 PM, Christofer Bogaso
> <bogaso.christofer at gmail.com> wrote:
>>
>> My modified function looks below :
>>
>> Lapply_me = function(X = X, FUN = FUN, Apply_MC = FALSE, ...) {
>> if (Apply_MC) {
>> return(mclapply(X, FUN, ...))
>> } else {
>> if (any(names(list(...)) == 'mc.cores')) {
>> myList = list(...)[!names(list(...)) %in% 'mc.cores']
>> }
>> return(lapply(X, FUN, myList))
>> }
>> }
>>
>> Here, I am not passing ... anymore rather passing myList
>>
>> On Sun, Mar 4, 2018 at 10:37 PM, Eric Berger <ericjberger at gmail.com>
>> wrote:
>> > Hi Christofer,
>> > Before you made the change that I suggested, your program was stopping
>> > at
>> > the statement: list(...) = list(..) .etc
>> > This means that it never tried to execute the statement:
>> > return(lapply(X,FUN,...))
>> > Now that you have made the change, it gets past the first statement and
>> > tries to execute the statement: return(lapply(X,FUN,...)).
>> > That attempt is generating the error message because whatever you are
>> > passing in as the FUN argument is not expecting extra arguments.
>> >
>> > HTH,
>> > Eric
>> >
>> >
>> > On Sun, Mar 4, 2018 at 6:52 PM, Christofer Bogaso
>> > <bogaso.christofer at gmail.com> wrote:
>> >>
>> >> @Eric - with this approach I am getting below error :
>> >>
>> >> Error in FUN(X[[i]], ...) : unused argument (list())
>> >>
>> >> On Sun, Mar 4, 2018 at 10:18 PM, Eric Berger <ericjberger at gmail.com>
>> >> wrote:
>> >> > Hi Christofer,
>> >> > You cannot assign to list(...). You can do the following
>> >> >
>> >> > myList <- list(...)[!names(list(...)) %in% 'mc.cores']
>> >> >
>> >> > HTH,
>> >> > Eric
>> >> >
>> >> > On Sun, Mar 4, 2018 at 6:38 PM, Christofer Bogaso
>> >> > <bogaso.christofer at gmail.com> wrote:
>> >> >>
>> >> >> Hi,
>> >> >>
>> >> >> As an example, I want to create below kind of custom Function which
>> >> >> either be mclapply pr lapply
>> >> >>
>> >> >> Lapply_me = function(X = X, FUN = FUN, ..., Apply_MC = FALSE) {
>> >> >> if (Apply_MC) {
>> >> >> return(mclapply(X, FUN, ...))
>> >> >> } else {
>> >> >> if (any(names(list(...)) == 'mc.cores')) {
>> >> >> list(...) = list(...)[!names(list(...)) %in% 'mc.cores']
>> >> >> }
>> >> >> return(lapply(X, FUN, ...))
>> >> >> }
>> >> >> }
>> >> >>
>> >> >> However when Apply_MC = FALSE it generates below error saying :
>> >> >>
>> >> >>   '...' used in an incorrect context
>> >> >>
>> >> >>
>> >> >> Appreciate if you can help me with the correct approach. Thanks,
>> >> >>
>> >> >>
>> >> >> On Sun, Mar 4, 2018 at 9:34 PM, Duncan Murdoch
>> >> >> <murdoch.duncan at gmail.com>
>> >> >> wrote:
>> >> >> > On 04/03/2018 10:39 AM, Christofer Bogaso wrote:
>> >> >> >>
>> >> >> >> Hi again,
>> >> >> >>
>> >> >> >> I am looking for some way to alternately use 2 related functions,
>> >> >> >> based on some ifelse() condition.
>> >> >> >>
>> >> >> >> For example, I have 2 functions mclapply() and lapply()
>> >> >> >>
>> >> >> >> However, mclapply() function has one extra parameter 'mc.cores'
>> >> >> >> which
>> >> >> >> lapply doesnt not have.
>> >> >> >>
>> >> >> >> I know when mc.cores = 1, these 2 functions are essentially same,
>> >> >> >> however I am looking for more general way to control them within
>> >> >> >> ifelse() constion
>> >> >> >>
>> >> >> >> Can someone please help me how can I use them within ifelse()
>> >> >> >> condition.
>> >> >> >
>> >> >> >
>> >> >> > Don't.  ifelse() usually evaluates *both* the true and false
>> >> >> > values,
>> >> >> > and
>> >> >> > then selects entries from each.  Just use an if statement.
>> >> >> >
>> >> >> > Duncan Murdoch
>> >> >>
>> >> >> ______________________________________________
>> >> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> >> >> https://stat.ethz.ch/mailman/listinfo/r-help
>> >> >> PLEASE do read the posting guide
>> >> >> http://www.R-project.org/posting-guide.html
>> >> >> and provide commented, minimal, self-contained, reproducible code.
>> >> >
>> >> >
>> >
>> >
>
>