[R] Calling a procedure
Bert Gunter
bgunter@4567 @end|ng |rom gm@||@com
Sun Sep 20 18:26:32 CEST 2020
Argument passing is fundamental, even more so when you write your own
functions, which any half-serious R user will want to do. What has
heretofore been discussed in this thread is not the whole story (e.g. there
are ... arguments and functions as binary operators, among other things).
See section 10 of the "Introduction to R" document that ships with R or any
other decent R tutorial of your choice. The R language definition is the
definitive reference (section 4 especially for this).
All imo of course.
Bert Gunter
"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Sun, Sep 20, 2020 at 8:57 AM Mark Leeds <markleeds2 using gmail.com> wrote:
> Hi Steven: Rui's detailed explanation was great. The way I think of it is,
> if you don't
> want to send the variables in with the same order as the formal
> arguments, then you
> better name them as you send them in.
>
>
>
>
>
> On Sun, Sep 20, 2020 at 7:23 AM Steven Yen <styen using ntu.edu.tw> wrote:
>
> > Thanks. So, to be safe, always a good idea to give the argument, e.g.,
> > q=1.96, log.p=FALSE, skipping mean=0 and sd=1 if not needed. Thanks.
> >
> > pnorm(q=1.96, log.p = FALSE)
> >
> > On 2020/9/20 下午 06:36, Rui Barradas wrote:
> > > Hello,
> > >
> > > You are making a confusion between
> > >
> > > 1. the formal argument log.p
> > > 2. the variable log.p
> > >
> > > In the function body, log.p is a variable that exists in the
> > > function's frame, not the formal argument of pnorm.
> > > The first and the 3rd calls that follow output the same value.
> > >
> > > try(x = 1.2, log.p = TRUE)$a
> > > try(x = 1.2, log.p = TRUE)$b
> > > try(x = 1.2, 1)$a
> > >
> > > This is because in the function
> > >
> > > a<-pnorm(x,log.p) # first call
> > >
> > > passes log.p as the *second* argument, not as a value for pnorm's
> > > formal argument log.p. Unless when named, the arguments are passed in
> > > the order they appear in the function's definition:
> > >
> > > pnorm(q, mean = 0, sd = 1, lower.tail = TRUE, log.p = FALSE)
> > >
> > > and that becomes
> > >
> > > a<-pnorm(x,TRUE) # first call
> > > a<-pnorm(x,1) # first call, coerced to numeric.
> > >
> > >
> > > Let me give another example. In the function that follows the default
> > > is z = FALSE.
> > >
> > > In the first call the name z is not the name of the argument, it's the
> > > name of a variable that exists in the .GlobalEnv.
> > >
> > > In the second call, z = z assign the formal argument z the value of
> > > the variable z.
> > >
> > >
> > > f <- function(x, y = 0, z = FALSE){
> > > a <- x
> > > b <- y
> > > d <- z
> > > list(a = a, b = b, d = d)
> > > }
> > > z <- 2
> > > f(1, z)
> > > f(1, z = z)
> > >
> > >
> > > Hope this helps,
> > >
> > > Rui Barradas
> > >
> > > Às 11:11 de 20/09/20, Steven Yen escreveu:
> > >> Can someone tell me a proper call to a procedure, in this case,
> > >> pnorm. In what follows, I had expected a = b, but they are not equal.
> > >> What are wrong with first call and second call? Thank you!
> > >>
> > >> try<-function(x,log.p=FALSE){
> > >> a<-pnorm(x,log.p) # first call
> > >> b<-pnorm(x,log.p=log.p) # second call
> > >> list(a=a,b=b)
> > >> }
> > >>
> > >> try(x=1.2,log.p=TRUE)$a
> > >> try(x=1.2,log.p=TRUE)$b
> > >>
> > >> ______________________________________________
> > >> R-help using 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.
> >
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> >
> > ______________________________________________
> > R-help using 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.
> >
>
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>
> ______________________________________________
> R-help using 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.
>
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