R help - Oct 2010 - Pasting function arguments and strings

Dear R community,

I am struggling a bit with a probably fairly simple task. I need to use some
already existing functions as argument for a new function that I am going to
create. 'dataset' is an argument, and it comprises objects named
'mean_test', 'sd_test', 'kurt_test' and so on.
'arg1' tells what object I
want (mean, sd, kurt) while 'arg2' tells what to do to the object taken
in
'arg1' (again could be mean, sd, but also any other operation/function).

I was thinking about something like:

myfunction<-function(dataset,arg1,arg2)

{

attach(dataset)
result=arg2(paste(arg1,"_test"))

return(result)

}

But this of course does not work! 'arg1' is of type closure and I cannot
set
it as character. Moreover, paste will create a string, and I do not think I
can pass a string to the function of 'arg2'. How should I do?

Thanks,
Marco
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If I understand you correctly, just arg2(arg1) will work fine...One of
the nice features of R.

Example:

f <- function(dat,fun=mean,...)
{
   fun(dat, ...) ## ... allows extra arguments to fun
}


f( rnorm(10), trim=.05) ## trimmed mean
x <- 1:10
f(x, fun = max,na.rm=TRUE)


Cheers,
Bert


On Wed, Oct 13, 2010 at 8:57 AM, Manta <mantino84 at libero.it>
wrote:
>
> Dear R community,
>
> I am struggling a bit with a probably fairly simple task. I need to use
some
> already existing functions as argument for a new function that I am going
to
> create. 'dataset' is an argument, and it comprises objects named
> 'mean_test', 'sd_test', 'kurt_test' and so on.
'arg1' tells what object I
> want (mean, sd, kurt) while 'arg2' tells what to do to the object
taken in
> 'arg1' (again could be mean, sd, but also any other
operation/function).
>
> I was thinking about something like:
>
> myfunction<-function(dataset,arg1,arg2)
>
> {
>
> attach(dataset)
> result=arg2(paste(arg1,"_test"))
>
> return(result)
>
> }
>
> But this of course does not work! 'arg1' is of type closure and I
cannot set
> it as character. Moreover, paste will create a string, and I do not think I
> can pass a string to the function of 'arg2'. How should I do?
>
> Thanks,
> Marco
> --
> View this message in context:
http://r.789695.n4.nabble.com/Pasting-function-arguments-and-strings-tp2993905p2993905.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>


-- 
Bert Gunter
Genentech Nonclinical Biostatistics