R help - Sep 2004 - defining a template for functions via do.call and substit ute.

Here's one not-so-straightforward way:
> f <- function(a, b) a + b
> flist <- as.list(f)
> names(flist)[1:2] <- c("x", "y")
> flist[[3]] <- do.call("substitute", list(body(f),
list(a=as.name("x"),
b=as.name("y"))))
> g <- as.function(flist)
> g
function (x, y) 
x + y

HTH,
Andy
> From: john.gavin at ubs.com
> 
> Hi,
> 
> Given a function
> 
>   fun <- function(a, b) a + b
> 
> how do I generate the function 'function(x, y) x + y'?
> 
> Working from the help files and Bill Venables' R-news article 
> (June 2002),
> I have tried various permutations with substitute without success. 
> e.g.
>   do.call("substitute", list(fun, list(a =
as.name("x"), b =
> as.name("y"))))
> 
> Regards,
> 
> John.
> 
> John Gavin <john.gavin at ubs.com>,
> Quantitative Risk Models and Statistics,
> UBS Investment Bank, 6th floor, 
> 100 Liverpool St., London EC2M 2RH, UK.
> Phone +44 (0) 207 567 4289
> Fax   +44 (0) 207 568 5352
> 
> Visit our website at http://www.ubs.com
> 
> This message contains confidential information and is 
> intend...{{dropped}}
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 
>

Or a slight modification

fun <- function(a, b) a+b
####
g <- function(){}
body(g) <- do.call("substitute", list(body(fun),
list(a=as.name("x"),
b=as.name("y"))))
formals(g) <- alist(x=, y=)
g

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/396887
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Liaw, Andy" <andy_liaw at merck.com>
To: <john.gavin at ubs.com>; <r-help at stat.math.ethz.ch>
Sent: Wednesday, September 29, 2004 2:13 PM
Subject: RE: [R] defining a template for functions via do.call and 
substit ute.

> Here's one not-so-straightforward way:
>
>> f <- function(a, b) a + b
>> flist <- as.list(f)
>> names(flist)[1:2] <- c("x", "y")
>> flist[[3]] <- do.call("substitute", list(body(f), 
>> list(a=as.name("x"),
> b=as.name("y"))))
>> g <- as.function(flist)
>> g
> function (x, y)
> x + y
>
> HTH,
> Andy
>
>> From: john.gavin at ubs.com
>>
>> Hi,
>>
>> Given a function
>>
>>   fun <- function(a, b) a + b
>>
>> how do I generate the function 'function(x, y) x + y'?
>>
>> Working from the help files and Bill Venables' R-news article
>> (June 2002),
>> I have tried various permutations with substitute without success.
>> e.g.
>>   do.call("substitute", list(fun, list(a =
as.name("x"), b >> as.name("y"))))
>>
>> Regards,
>>
>> John.
>>
>> John Gavin <john.gavin at ubs.com>,
>> Quantitative Risk Models and Statistics,
>> UBS Investment Bank, 6th floor,
>> 100 Liverpool St., London EC2M 2RH, UK.
>> Phone +44 (0) 207 567 4289
>> Fax   +44 (0) 207 568 5352
>>
>> Visit our website at http://www.ubs.com
>>
>> This message contains confidential information and is
>> intend...{{dropped}}
>>
>> ______________________________________________
>> R-help at stat.math.ethz.ch mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide!
>> http://www.R-project.org/posting-guide.html
>>
>>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
>

THE FLAW!  :-(

-- Bert 
> -----Original Message-----
> From: Liaw, Andy [mailto:andy_liaw at merck.com] 
> Sent: Wednesday, September 29, 2004 10:11 AM
> To: 'Berton Gunter'
> Subject: RE: [R] defining a template for functions via 
> do.call and substit ute.
> 
> Bert,
> 
> I thought about that, too, but I believe that approach is not 
> as safe, as
> one could run into trouble if the body of the function has 
> something like
> aCupOfCofee + someCream, which would ended up as xCupOfCofee 
> + someCrexm...
> 
> Cheers,
> Andy