Evaluation of variable assigned to a function name

Note that I will call my function or user-defined function in bar function to
have the value that my or user-defined function returns. So how can these
function be invoked? Can it be like this?

bar<- function(arglist, foo){
      if(missing(foo)) {
            foo<- my.func
          v = my.func(x = 2)
      }
     else{
          foo<- my.func.user

          v<- do.call(foo, arglist) # since arglist is not known in advance
     }
      return(v*3)
}



----- Original Message ----
From: Uwe Ligges<ligges at statistik.tu-dortmund.de>
To: carol white<wht_crl at yahoo.com>
Cc: r-help at stat.math.ethz.ch
Sent: Mon, January 10, 2011 3:04:19 PM
Subject: Re: [R] Evaluation of variable assigned to a function name



On 10.01.2011 14:56, carol white wrote:

Let the following definitions:


# my definition
my.func<- function (x,y,z){
....
return (v)
}

# user-defined definition
my.func<- function (x){
...
return(v)
}

Considering that my.func can have different parameters but always return a
vector, how to use v in bar by initializing parameters when calling my.func 

=
2 or a = 3,y=4,z=5)? How can my.func could be invoked in bar and v could be
used?

Well, both versions will need the same number of arguments unless you
want to pass the as well. Example:

bar<- function(arglist, foo){
      if(missing(foo)) foo<- my.func
      v<- do.call(foo, arglist)
      return(v*3)
}

my.func<- function(x,y,z){
      return(x+y+z)
}

my.func.user<- function(x){
     return(x)
}


Then you can do, e.g.:

bar(arglist=list(x=1, y=2, z=3))

bar(arglist=list(x=1), foo=my.func.user)


Hope this clarifies the idea.

Best,
Uwe

bar<- function(x, ....., foo){

       if(missing(foo)) foo<- Namespace::my.func
       .....
}

----- Original Message ----
From: Uwe Ligges<ligges at statistik.tu-dortmund.de>
To: carol white<wht_crl at yahoo.com>
Cc: r-help at stat.math.ethz.ch
Sent: Mon, January 10, 2011 2:48:04 PM
Subject: Re: [R] Evaluation of variable assigned to a function name



On 10.01.2011 14:39, carol white wrote:

In fact, what the function is returning is the most important. So knowing

that

the parameters and the number of parameters of my.func defined by the user
could
be different from one definition to another, how to use what my.func returns

in

other functions? Moreover, if the function is defined by the user in an R
session, it is then defined globally. In this case, does it need to be 

as
a parameter? Note that my.func defined by me is loaded before.

It depends.

1. The output of a function can always be wrapped in a list.
2. You should always pass objects that you want to use in another
environment unless you really know what you are doing - and reading does
not suggest you are too sure about it.
3. In this case, if your package has a Namespace, your own function
rather than a user generated one in the .GlobalEnv will be found.

Note that defining stuff in .GlobalEnv and relying on the fact that this
version is found by another function would imply you really have to get
it from the specific environment.

Best,
Uwe

Carol



----- Original Message ----
From: Uwe Ligges<ligges at statistik.tu-dortmund.de>
To: carol white<wht_crl at yahoo.com>
Cc: r-help at stat.math.ethz.ch
Sent: Mon, January 10, 2011 2:11:48 PM
Subject: Re: [R] Evaluation of variable assigned to a function name

Wel, just let the user give the function in form of an argument, say
"foo", and use your code so that


bar<- function(x, ....., foo){
       if(missing(foo)) foo<- Namespace::my.func
       .....
}


but perhaps I misunderstood your question.

Uwe Ligges



On 10.01.2011 13:47, carol white wrote:

Hi,
I have defined a function (my.func) which is used as parameter (f) of

another

function. As I want to give the user the possibility to define his own

function

instead of my.func, how can I find out if in other functions, the parameter

f

has the my.func value (if the user has defined a new function or not)?


Moreover, I think I should impose to the user to use another function name

than

my.func for this (?). Or a boolean variable is better to be used to 

if

my function (my.func) or user-defined function is used?

Thanks

Carol