Re: [R] Construct a function with argments specified by an R expression
This is kind of fun, although it gets a bit far into the realm of obfuscation…
It also seems to work to do
> arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> f <- function()"hello"
> formals(f) <- sapply(arg_names,\(.)unname(alist(x=)))
> f
function (x, y, a1, a2, a3, b1, b2, b3) “hello”
- pd
> On 26 Oct 2025, at 15.47, Gabor Grothendieck wrote:
>
> This can be simplified slightly to
>
> # inputs
> arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> f <- function() {}
>
> arg <- alist(x = )
> formals(f) <- setNames(rep(arg, length(arg_names)), arg_names)
> f
>
> ## function (x, y, a1, a2, a3, b1, b2, b3)
> ## {
> ## }
>
> On Sun, Oct 26, 2025 at 10:41 AM Gabor Grothendieck
> wrote:
>>
>> Define the names and a prototype and then use formals(f) <- ... as shown.
>>
>> # inputs
>> arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
>> f <- function() {}
>>
>> arg <- alist(x = )
>> formals(f) <- setNames(c(arg, rep(arg, length(arg_names)-1)), arg_names)
>> f
>>
>> giving
>>
>> function (x, y, a1, a2, a3, b1, b2, b3)
>> {
>> }
>>
>> On Fri, Oct 24, 2025 at 10:23 PM Rolf Turner wrote:
>>>
>>>
>>> I want to build a function (say "buildFn") to *return* a function of the
>>> form
>>>
>>>foo(x,y,a1, ... an, b1, ..., bn)
>>>
>>> where the arguments ai and bi are given in the form of a list created
>>> in R. E.g. I'd like to be able to say
>>>
>>> argnms <- c(paste0("a",1:3),paste0("b",1:3"))
>>> foo <- buildFn(argnms)
>>>
>>> with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
>>>
>>> I thought I might be able to do this using "formals<-" but I cannot get
>>> this to work. i could provide more detail of what I've tried, but it's
>>> probably not worth it.
>>>
>>> Can anyone steer me in the right direction? Thanks.
>>>
>>> cheers,
>>>
>>> Rolf Turner
>>>
>>> --
>>> Honorary Research Fellow
>>> Department of Statistics
>>> University of Auckland
>>> Stats. Dep't. (secretaries) phone:
>>> +64-9-373-7599 ext. 89622
>>> Home phone: +64-9-480-4619
>>>
>>> __
>>> [email protected] mailing list -- To UNSUBSCRIBE and more, see
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> https://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>
>> --
>> Statistics & Software Consulting
>> GKX Group, GKX Associates Inc.
>> tel: 1-877-GKX-GROUP
>> email: ggrothendieck at gmail.com
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business SchoolSolbjerg Plads 3, 2000
Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: [email protected] Priv: [email protected]
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Re: [R] Construct a function with argments specified by an R expression
Well, in the spirit of Rolf's original request, a slightly different
version of Gabor's/Duncan's suggestions is:
buildFn <- function(argnms){
f <- function(){
## whatever
}
## produce a named (regular) list (of NA's here) with the desired names for
formals()
formals(f) <- setNames( as.list(c(rep(NA, length(argnms) + 2))),
nm = c('x', 'y', argnms))
f
}
Note that this requires/gives default arguments (NA's here) for everything,
which may be undesirable:
> foo <- buildFn(argnms = argnms)
> foo
function (x = NA, y = NA, a1 = NA, a2 = NA, a3 = NA, b1 = NA,
b2 = NA, b3 = NA)
{
}
Cheers,
Bert
On Sun, Oct 26, 2025 at 11:14 AM Gabor Grothendieck
wrote:
> Here is an approach using as.function.formula from gsubfn:
>
> library (gsubfn)
>
> # inputs
> arg_names <- head(letters)
> f <- function() {}
>
> formals(f) <- formals(as.function(reformulate(arg_names)))
> f
>
> On Sun, Oct 26, 2025 at 10:47 AM Gabor Grothendieck
> wrote:
> >
> > This can be simplified slightly to
> >
> > # inputs
> > arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> > f <- function() {}
> >
> > arg <- alist(x = )
> > formals(f) <- setNames(rep(arg, length(arg_names)), arg_names)
> > f
> >
> > ## function (x, y, a1, a2, a3, b1, b2, b3)
> > ## {
> > ## }
> >
> > On Sun, Oct 26, 2025 at 10:41 AM Gabor Grothendieck
> > wrote:
> > >
> > > Define the names and a prototype and then use formals(f) <- ... as
> shown.
> > >
> > > # inputs
> > > arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> > > f <- function() {}
> > >
> > > arg <- alist(x = )
> > > formals(f) <- setNames(c(arg, rep(arg, length(arg_names)-1)),
> arg_names)
> > > f
> > >
> > > giving
> > >
> > > function (x, y, a1, a2, a3, b1, b2, b3)
> > > {
> > > }
> > >
> > > On Fri, Oct 24, 2025 at 10:23 PM Rolf Turner
> wrote:
> > > >
> > > >
> > > > I want to build a function (say "buildFn") to *return* a function of
> the
> > > > form
> > > >
> > > > foo(x,y,a1, ... an, b1, ..., bn)
> > > >
> > > > where the arguments ai and bi are given in the form of a list created
> > > > in R. E.g. I'd like to be able to say
> > > >
> > > > argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> > > > foo <- buildFn(argnms)
> > > >
> > > > with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2,
> b3.
> > > >
> > > > I thought I might be able to do this using "formals<-" but I cannot
> get
> > > > this to work. i could provide more detail of what I've tried, but
> it's
> > > > probably not worth it.
> > > >
> > > > Can anyone steer me in the right direction? Thanks.
> > > >
> > > > cheers,
> > > >
> > > > Rolf Turner
> > > >
> > > > --
> > > > Honorary Research Fellow
> > > > Department of Statistics
> > > > University of Auckland
> > > > Stats. Dep't. (secretaries) phone:
> > > > +64-9-373-7599 ext. 89622
> > > > Home phone: +64-9-480-4619
> > > >
> > > > __
> > > > [email protected] mailing list -- To UNSUBSCRIBE and more, see
> > > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > > PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> > > > and provide commented, minimal, self-contained, reproducible code.
> > >
> > >
> > >
> > > --
> > > Statistics & Software Consulting
> > > GKX Group, GKX Associates Inc.
> > > tel: 1-877-GKX-GROUP
> > > email: ggrothendieck at gmail.com
> >
> >
> >
> > --
> > Statistics & Software Consulting
> > GKX Group, GKX Associates Inc.
> > tel: 1-877-GKX-GROUP
> > email: ggrothendieck at gmail.com
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
Here is an approach using as.function.formula from gsubfn:
library (gsubfn)
# inputs
arg_names <- head(letters)
f <- function() {}
formals(f) <- formals(as.function(reformulate(arg_names)))
f
On Sun, Oct 26, 2025 at 10:47 AM Gabor Grothendieck
wrote:
>
> This can be simplified slightly to
>
> # inputs
> arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> f <- function() {}
>
> arg <- alist(x = )
> formals(f) <- setNames(rep(arg, length(arg_names)), arg_names)
> f
>
> ## function (x, y, a1, a2, a3, b1, b2, b3)
> ## {
> ## }
>
> On Sun, Oct 26, 2025 at 10:41 AM Gabor Grothendieck
> wrote:
> >
> > Define the names and a prototype and then use formals(f) <- ... as shown.
> >
> > # inputs
> > arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> > f <- function() {}
> >
> > arg <- alist(x = )
> > formals(f) <- setNames(c(arg, rep(arg, length(arg_names)-1)), arg_names)
> > f
> >
> > giving
> >
> > function (x, y, a1, a2, a3, b1, b2, b3)
> > {
> > }
> >
> > On Fri, Oct 24, 2025 at 10:23 PM Rolf Turner wrote:
> > >
> > >
> > > I want to build a function (say "buildFn") to *return* a function of the
> > > form
> > >
> > > foo(x,y,a1, ... an, b1, ..., bn)
> > >
> > > where the arguments ai and bi are given in the form of a list created
> > > in R. E.g. I'd like to be able to say
> > >
> > > argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> > > foo <- buildFn(argnms)
> > >
> > > with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
> > >
> > > I thought I might be able to do this using "formals<-" but I cannot get
> > > this to work. i could provide more detail of what I've tried, but it's
> > > probably not worth it.
> > >
> > > Can anyone steer me in the right direction? Thanks.
> > >
> > > cheers,
> > >
> > > Rolf Turner
> > >
> > > --
> > > Honorary Research Fellow
> > > Department of Statistics
> > > University of Auckland
> > > Stats. Dep't. (secretaries) phone:
> > > +64-9-373-7599 ext. 89622
> > > Home phone: +64-9-480-4619
> > >
> > > __
> > > [email protected] mailing list -- To UNSUBSCRIBE and more, see
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide
> > > https://www.R-project.org/posting-guide.html
> > > and provide commented, minimal, self-contained, reproducible code.
> >
> >
> >
> > --
> > Statistics & Software Consulting
> > GKX Group, GKX Associates Inc.
> > tel: 1-877-GKX-GROUP
> > email: ggrothendieck at gmail.com
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
I will correct myself. "Special features of the languages" is not the same
as "computing on the language." So my comment misunderstood your meaning.
Bert
On Sun, Oct 26, 2025 at 8:21 AM Bert Gunter wrote:
> I disagree. I see "formals() <- " as a way to compute on **functions**,
> which are first class *objects* in R, as in any functional programming
> language. This is not computing on the language as I understand the term
> -- substitute() and friends are, i.e. anything where eval() is needed to
> get a result.
>
> Cheers,
> Bert
>
>
> On Sun, Oct 26, 2025 at 7:36 AM Richard O'Keefe wrote:
>
>> Can I just mention the quick-and-dirty way that will get the job done?
>> Not as elegant as use the special features of the language *meant* for
>> this kind of job,
>> but suitable for a bear of very little brain.
>>
>> 1. Write a function that constructs the code you want as text, written
>> to a file.
>> 2. source() the file.'
>>
>> On Sat, 25 Oct 2025 at 15:23, Rolf Turner wrote:
>> >
>> >
>> > I want to build a function (say "buildFn") to *return* a function of the
>> > form
>> >
>> > foo(x,y,a1, ... an, b1, ..., bn)
>> >
>> > where the arguments ai and bi are given in the form of a list created
>> > in R. E.g. I'd like to be able to say
>> >
>> > argnms <- c(paste0("a",1:3),paste0("b",1:3"))
>> > foo <- buildFn(argnms)
>> >
>> > with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
>> >
>> > I thought I might be able to do this using "formals<-" but I cannot get
>> > this to work. i could provide more detail of what I've tried, but it's
>> > probably not worth it.
>> >
>> > Can anyone steer me in the right direction? Thanks.
>> >
>> > cheers,
>> >
>> > Rolf Turner
>> >
>> > --
>> > Honorary Research Fellow
>> > Department of Statistics
>> > University of Auckland
>> > Stats. Dep't. (secretaries) phone:
>> > +64-9-373-7599 ext. 89622
>> > Home phone: +64-9-480-4619
>> >
>> > __
>> > [email protected] mailing list -- To UNSUBSCRIBE and more, see
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide
>> https://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>>
>> __
>> [email protected] mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> https://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
[[alternative HTML version deleted]]
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
I disagree. I see "formals() <- " as a way to compute on **functions**,
which are first class *objects* in R, as in any functional programming
language. This is not computing on the language as I understand the term
-- substitute() and friends are, i.e. anything where eval() is needed to
get a result.
Cheers,
Bert
On Sun, Oct 26, 2025 at 7:36 AM Richard O'Keefe wrote:
> Can I just mention the quick-and-dirty way that will get the job done?
> Not as elegant as use the special features of the language *meant* for
> this kind of job,
> but suitable for a bear of very little brain.
>
> 1. Write a function that constructs the code you want as text, written
> to a file.
> 2. source() the file.'
>
> On Sat, 25 Oct 2025 at 15:23, Rolf Turner wrote:
> >
> >
> > I want to build a function (say "buildFn") to *return* a function of the
> > form
> >
> > foo(x,y,a1, ... an, b1, ..., bn)
> >
> > where the arguments ai and bi are given in the form of a list created
> > in R. E.g. I'd like to be able to say
> >
> > argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> > foo <- buildFn(argnms)
> >
> > with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
> >
> > I thought I might be able to do this using "formals<-" but I cannot get
> > this to work. i could provide more detail of what I've tried, but it's
> > probably not worth it.
> >
> > Can anyone steer me in the right direction? Thanks.
> >
> > cheers,
> >
> > Rolf Turner
> >
> > --
> > Honorary Research Fellow
> > Department of Statistics
> > University of Auckland
> > Stats. Dep't. (secretaries) phone:
> > +64-9-373-7599 ext. 89622
> > Home phone: +64-9-480-4619
> >
> > __
> > [email protected] mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
[[alternative HTML version deleted]]
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
This can be simplified slightly to
# inputs
arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
f <- function() {}
arg <- alist(x = )
formals(f) <- setNames(rep(arg, length(arg_names)), arg_names)
f
## function (x, y, a1, a2, a3, b1, b2, b3)
## {
## }
On Sun, Oct 26, 2025 at 10:41 AM Gabor Grothendieck
wrote:
>
> Define the names and a prototype and then use formals(f) <- ... as shown.
>
> # inputs
> arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
> f <- function() {}
>
> arg <- alist(x = )
> formals(f) <- setNames(c(arg, rep(arg, length(arg_names)-1)), arg_names)
> f
>
> giving
>
> function (x, y, a1, a2, a3, b1, b2, b3)
> {
> }
>
> On Fri, Oct 24, 2025 at 10:23 PM Rolf Turner wrote:
> >
> >
> > I want to build a function (say "buildFn") to *return* a function of the
> > form
> >
> > foo(x,y,a1, ... an, b1, ..., bn)
> >
> > where the arguments ai and bi are given in the form of a list created
> > in R. E.g. I'd like to be able to say
> >
> > argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> > foo <- buildFn(argnms)
> >
> > with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
> >
> > I thought I might be able to do this using "formals<-" but I cannot get
> > this to work. i could provide more detail of what I've tried, but it's
> > probably not worth it.
> >
> > Can anyone steer me in the right direction? Thanks.
> >
> > cheers,
> >
> > Rolf Turner
> >
> > --
> > Honorary Research Fellow
> > Department of Statistics
> > University of Auckland
> > Stats. Dep't. (secretaries) phone:
> > +64-9-373-7599 ext. 89622
> > Home phone: +64-9-480-4619
> >
> > __
> > [email protected] mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > https://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
Define the names and a prototype and then use formals(f) <- ... as shown.
# inputs
arg_names <- c("x", "y", paste0("a", 1:3), paste0("b", 1:3))
f <- function() {}
arg <- alist(x = )
formals(f) <- setNames(c(arg, rep(arg, length(arg_names)-1)), arg_names)
f
giving
function (x, y, a1, a2, a3, b1, b2, b3)
{
}
On Fri, Oct 24, 2025 at 10:23 PM Rolf Turner wrote:
>
>
> I want to build a function (say "buildFn") to *return* a function of the
> form
>
> foo(x,y,a1, ... an, b1, ..., bn)
>
> where the arguments ai and bi are given in the form of a list created
> in R. E.g. I'd like to be able to say
>
> argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> foo <- buildFn(argnms)
>
> with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
>
> I thought I might be able to do this using "formals<-" but I cannot get
> this to work. i could provide more detail of what I've tried, but it's
> probably not worth it.
>
> Can anyone steer me in the right direction? Thanks.
>
> cheers,
>
> Rolf Turner
>
> --
> Honorary Research Fellow
> Department of Statistics
> University of Auckland
> Stats. Dep't. (secretaries) phone:
> +64-9-373-7599 ext. 89622
> Home phone: +64-9-480-4619
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
Can I just mention the quick-and-dirty way that will get the job done?
Not as elegant as use the special features of the language *meant* for
this kind of job,
but suitable for a bear of very little brain.
1. Write a function that constructs the code you want as text, written
to a file.
2. source() the file.'
On Sat, 25 Oct 2025 at 15:23, Rolf Turner wrote:
>
>
> I want to build a function (say "buildFn") to *return* a function of the
> form
>
> foo(x,y,a1, ... an, b1, ..., bn)
>
> where the arguments ai and bi are given in the form of a list created
> in R. E.g. I'd like to be able to say
>
> argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> foo <- buildFn(argnms)
>
> with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
>
> I thought I might be able to do this using "formals<-" but I cannot get
> this to work. i could provide more detail of what I've tried, but it's
> probably not worth it.
>
> Can anyone steer me in the right direction? Thanks.
>
> cheers,
>
> Rolf Turner
>
> --
> Honorary Research Fellow
> Department of Statistics
> University of Auckland
> Stats. Dep't. (secretaries) phone:
> +64-9-373-7599 ext. 89622
> Home phone: +64-9-480-4619
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
__
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
On Sat, 25 Oct 2025 06:24:48 -0400
Duncan Murdoch wrote:
> Another way to do this is to make a prototype and then modify it.
> For example,
>
>foo <- function(x, y, others) {
> # the body can be anything, we won't touch it
>}
>
>args <- formals(foo)
>
># Make extra copies of the 3rd argument
>args[3:(2 + length(argnms))] <- args[3]
>
># Set the names of the new ones (or use Iris's code to set all the
> names, your choice)
>
>names(args)[3:(2 + length(argnms))] <- argnms
>
>formals(foo) <- args
>
> Duncan Murdoch
That saves my having to worry about quote() and expr. Ta.
cheers,
Rolf
--
Honorary Research Fellow
Department of Statistics
University of Auckland
Stats. Dep't. (secretaries) phone:
+64-9-373-7599 ext. 89622
Home phone: +64-9-480-4619
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
Another way to do this is to make a prototype and then modify it. For
example,
foo <- function(x, y, others) {
# the body can be anything, we won't touch it
}
args <- formals(foo)
# Make extra copies of the 3rd argument
args[3:(2 + length(argnms))] <- args[3]
# Set the names of the new ones (or use Iris's code to set all the
names, your choice)
names(args)[3:(2 + length(argnms))] <- argnms
formals(foo) <- args
Duncan Murdoch
On 2025-10-24 11:17 p.m., Rolf Turner wrote:
On Fri, 24 Oct 2025 22:31:53 -0400
Iris Simmons wrote:
I would start by making a list of the desired length, where each
element is the missing argument:
f <- rep(list(quote(expr = )), 2 + length(argnms))
then add names to the list:
names(f) <- c("x", "y", argnms)
and then use formals<-
formals(foo) <- f
Wow! That was fast! And it seems to do exactly what I want.
What I was missing, I guess, was the quote(expr = ) structure. I have
never really understood quote(), nor expr() either. I'll just treat it
as a black box for now.
Although, I would ask if you're certain that this is actually what
you want to do. It's usually a bad idea to have variable names that
you don't know. I'd to think it'd be better to have the default
argument:
a = list()
and supply a list of `a` values instead of several `a` arguments.
Yes I understand that that would be the "sensible" approach but it
doesn't work in the context with which I am confronted.
I have more work to do before I get the approach that I've envisaged up
and running.
I may inflict more questions upon you later. (No good deed goes
unpunished! 🙂️)
cheers,
Rolf
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
On Fri, 24 Oct 2025 22:31:53 -0400
Iris Simmons wrote:
> I would start by making a list of the desired length, where each
> element is the missing argument:
>
> f <- rep(list(quote(expr = )), 2 + length(argnms))
>
> then add names to the list:
>
> names(f) <- c("x", "y", argnms)
>
> and then use formals<-
>
> formals(foo) <- f
Wow! That was fast! And it seems to do exactly what I want.
What I was missing, I guess, was the quote(expr = ) structure. I have
never really understood quote(), nor expr() either. I'll just treat it
as a black box for now.
> Although, I would ask if you're certain that this is actually what
> you want to do. It's usually a bad idea to have variable names that
> you don't know. I'd to think it'd be better to have the default
> argument:
>
> a = list()
>
> and supply a list of `a` values instead of several `a` arguments.
Yes I understand that that would be the "sensible" approach but it
doesn't work in the context with which I am confronted.
I have more work to do before I get the approach that I've envisaged up
and running.
I may inflict more questions upon you later. (No good deed goes
unpunished! 🙂️)
cheers,
Rolf
--
Honorary Research Fellow
Department of Statistics
University of Auckland
Stats. Dep't. (secretaries) phone:
+64-9-373-7599 ext. 89622
Home phone: +64-9-480-4619
__
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Construct a function with argments specified by an R expression
I would start by making a list of the desired length, where each element is
the missing argument:
f <- rep(list(quote(expr = )), 2 + length(argnms))
then add names to the list:
names(f) <- c("x", "y", argnms)
and then use formals<-
formals(foo) <- f
Although, I would ask if you're certain that this is actually what you want
to do. It's usually a bad idea to have variable names that you don't know.
I'd to think it'd be better to have the default argument:
a = list()
and supply a list of `a` values instead of several `a` arguments.
On Fri, Oct 24, 2025, 22:23 Rolf Turner wrote:
>
> I want to build a function (say "buildFn") to *return* a function of the
> form
>
> foo(x,y,a1, ... an, b1, ..., bn)
>
> where the arguments ai and bi are given in the form of a list created
> in R. E.g. I'd like to be able to say
>
> argnms <- c(paste0("a",1:3),paste0("b",1:3"))
> foo <- buildFn(argnms)
>
> with the resulting "foo" having arguments x, y, a1, a2, a3, b1, b2, b3.
>
> I thought I might be able to do this using "formals<-" but I cannot get
> this to work. i could provide more detail of what I've tried, but it's
> probably not worth it.
>
> Can anyone steer me in the right direction? Thanks.
>
> cheers,
>
> Rolf Turner
>
> --
> Honorary Research Fellow
> Department of Statistics
> University of Auckland
> Stats. Dep't. (secretaries) phone:
> +64-9-373-7599 ext. 89622
> Home phone: +64-9-480-4619
>
> __
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
