R help - Aug 2009 - Using 'field names' of a data.frame in a function

I may be doing this wrong!  but I have a function which I have simplified a lot
below.  I want to pass some 'field names' of a data-frame to the
function for it to then do some manipulation of.

Here's my code:
#build a simple dataset
 mydataset = data.frame (
ages=c('40-49','40-49','40-49','30-39','50-59','50-59','60-69','50-59'),
sex =
c("M","F","F","M","F","F","M","M"))

#build a simple function
 myfunc <- function (categories) {
   table (categories)
 }

#call the function
myfunc (c(mydataset$ages, mydataset$sex))

==
My output I am getting is:
categories
1 2 3 4
5 7 3 1

But what I'm expecting is:
table (mydataset$ages, mydataset$sex)

        F M
  30-39 0 1
  40-49 2 1
  50-59 2 1
  60-69 0 1


Calling the function as:  myfunc ("mydataset$ages, mydataset$sex")
doesn't work either and nor does myfunc (c("mydataset$ages",
"mydataset$sex"))

Now in the simple version above I could make the function (category1, category2)
and then call table (category1, category2) - but what if I might have a category
3, category 4 etc... How can I pass the dataset name to the function without it
trying to actually pass the data to the function?  I've also tried paste -
but perhaps I'm mis-using it?

Many thanks for help in advance

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Try this:
myfunc <- function(...)table(...)
with(mydataset, myfunc(ages, sex))

On Thu, Aug 6, 2009 at 4:50 PM, Polwart Calum (County Durham and Darlington
NHS Foundation Trust) <calum.polwart@nhs.net> wrote:
> I may be doing this wrong!  but I have a function which I have simplified a
> lot below.  I want to pass some 'field names' of a data-frame to
the
> function for it to then do some manipulation of.
>
> Here's my code:
> #build a simple dataset
>  mydataset = data.frame (
>
ages=c('40-49','40-49','40-49','30-39','50-59','50-59','60-69','50-59'),
>  sex =
c("M","F","F","M","F","F","M","M"))
>
> #build a simple function
>  myfunc <- function (categories) {
>   table (categories)
>  }
>
> #call the function
> myfunc (c(mydataset$ages, mydataset$sex))
>
> ==>
> My output I am getting is:
> categories
> 1 2 3 4
> 5 7 3 1
>
> But what I'm expecting is:
> table (mydataset$ages, mydataset$sex)
>
>        F M
>  30-39 0 1
>  40-49 2 1
>  50-59 2 1
>  60-69 0 1
>
>
> Calling the function as:  myfunc ("mydataset$ages,
mydataset$sex") doesn't
> work either and nor does myfunc (c("mydataset$ages",
"mydataset$sex"))
>
> Now in the simple version above I could make the function (category1,
> category2) and then call table (category1, category2) - but what if I might
> have a category 3, category 4 etc... How can I pass the dataset name to the
> function without it trying to actually pass the data to the function? 
I've
> also tried paste - but perhaps I'm mis-using it?
>
> Many thanks for help in advance
>
>
>
********************************************************************************************************************
>
> This message may contain confidential information. If ...{{dropped:20}}