R help - Oct 2009 - How do I access with the name of a (passed) function

How would I do something like this:

f <- function(x, g) {
  s <- as.character(g)               # THIS DOES NOT WORK
  sprintf("The %s of x is %.0f\n", s, g(x))
}

f(c(2,3,4), "median")
f(c(2,3,4), "mean")

and get the results 

   "The median of x is 3"
   "The mean of x is 3"

-- 
Ajay Shah                                      http://www.mayin.org/ajayshah  
ajayshah at mayin.org                            
http://ajayshahblog.blogspot.com
<*(:-? - wizard who doesn't know the answer.

Try this:
> show.name <- function(x) deparse(substitute(x))
> show.name(pi)
[1] "pi"


On Sat, Oct 17, 2009 at 7:26 AM, Ajay Shah <ajayshah at mayin.org>
wrote:
> How would I do something like this:
>
> f <- function(x, g) {
> ?s <- as.character(g) ? ? ? ? ? ? ? # THIS DOES NOT WORK
> ?sprintf("The %s of x is %.0f\n", s, g(x))
> }
>
> f(c(2,3,4), "median")
> f(c(2,3,4), "mean")
>
> and get the results
>
> ? "The median of x is 3"
> ? "The mean of x is 3"
>
> --
> Ajay Shah ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
?http://www.mayin.org/ajayshah
> ajayshah at mayin.org ? ? ? ? ? ? ? ? ? ? ? ? ? ?
http://ajayshahblog.blogspot.com
> <*(:-? - wizard who doesn't know the answer.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>

On 17/10/2009 7:26 AM, Ajay Shah wrote:
> How would I do something like this:
> 
> f <- function(x, g) {
>   s <- as.character(g)               # THIS DOES NOT WORK
>   sprintf("The %s of x is %.0f\n", s, g(x))
> }
Gabor showed you how to do it if you pass an expression which evaluates 
to a function.  If you want to pass an expression that returns a 
character string as below, use

if (is.character(g)) {
   s <- g
   g <- get(s, parent.frame()) # gets it from the caller's frame
}
> 
> f(c(2,3,4), "median")
> f(c(2,3,4), "mean")
> 
> and get the results 
> 
>    "The median of x is 3"
>    "The mean of x is 3"
> 
Duncan Murdoch