R help - Apr 2003 - creating function bodies using body()

I'm having trouble figuring out how to create a function using
"body<-"
().  The help file for body() says that the argument should be a list of
R expressions.  However if I try that I get an error:
> tmpfun <- function(a, b=2){}
> body(tmpfun) <- list(expression(z <- a + b),expression(z^2))
Error in as.function.default(c(formals(f), value), envir) :
        invalid formal argument list for "function"

Can someone give me a simple example for doing this?  Thanks!

R. Woodrow Setzer, Jr.                        Phone: (919) 541-0128
Experimental Toxicology Division             Fax:  (919) 541-4284
Pharmacokinetics Branch
NHEERL B143-05; US EPA; RTP, NC 27711

This apparently worked:
> body(f) <- expression({x^2; x+3})
> f
function (x) 
{
    x^2
    x + 3
}

HTH,
Andy
> -----Original Message-----
> From: Setzer.Woodrow at epamail.epa.gov
> [mailto:Setzer.Woodrow at epamail.epa.gov]
> Sent: Friday, April 04, 2003 5:06 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] creating function bodies using body()
> 
> 
> I'm having trouble figuring out how to create a function 
> using "body<-"
> ().  The help file for body() says that the argument should 
> be a list of
> R expressions.  However if I try that I get an error:
> 
> > tmpfun <- function(a, b=2){}
> > body(tmpfun) <- list(expression(z <- a + b),expression(z^2))
> Error in as.function.default(c(formals(f), value), envir) :
>         invalid formal argument list for "function"
> 
> Can someone give me a simple example for doing this?  Thanks!
> 
> R. Woodrow Setzer, Jr.                        Phone: (919) 541-0128
> Experimental Toxicology Division             Fax:  (919) 541-4284
> Pharmacokinetics Branch
> NHEERL B143-05; US EPA; RTP, NC 27711
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 

------------------------------------------------------------------------------

Defining a function is much simpler than that:

tmpfun <- function(a, b=2)
 {  z <- a = b
    z^2         }    #  returns (a + b)^2

But maybe you want the advertised syntax to work.  Please
pardon if I've misjudged the depth of your question.  I've
never tried to use  body().

-  tom blackwell  -  u michigan medical school  -  ann arbor  -

On Fri, 4 Apr 2003 Setzer.Woodrow at epamail.epa.gov wrote:
> I'm having trouble figuring out how to create a function using
"body<-"
> ().  The help file for body() says that the argument should be a list of
> R expressions.  However if I try that I get an error:
>
> > tmpfun <- function(a, b=2){}
> > body(tmpfun) <- list(expression(z <- a + b),expression(z^2))
> Error in as.function.default(c(formals(f), value), envir) :
>         invalid formal argument list for "function"
>
> Can someone give me a simple example for doing this?  Thanks!
>
> R. Woodrow Setzer, Jr.                        Phone: (919) 541-0128
> Experimental Toxicology Division             Fax:  (919) 541-4284
> Pharmacokinetics Branch
> NHEERL B143-05; US EPA; RTP, NC 27711

Setzer.Woodrow at epamail.epa.gov writes:
> I'm having trouble figuring out how to create a function using
"body<-"
> ().  The help file for body() says that the argument should be a list of
> R expressions.  However if I try that I get an error:
> 
> > tmpfun <- function(a, b=2){}
> > body(tmpfun) <- list(expression(z <- a + b),expression(z^2))
> Error in as.function.default(c(formals(f), value), envir) :
>         invalid formal argument list for "function"
> 
> Can someone give me a simple example for doing this?  Thanks!
Like this:
> tmpfun <- function(a, b=2){}
> body(tmpfun) <- quote({z <- a + b; z^2})
> tmpfun(3)
[1] 25

And yes, that help page could do with a rewrite...

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907