[R] Evaluation of variable assigned to a function name

[Uwe Ligges]

On 10.01.2011 16:41, carol white wrote:
> 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

The line abopve does nt make sense now, the rest seems to be fine.

Uwe


>           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 (x
>> =
>> 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 passed
>>> 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 indicate
>>> if
>>>> my function (my.func) or user-defined function is used?
>>>>
>>>> Thanks
>>>>
>>>> Carol
>>>>
>>>> ______________________________________________
>>>> 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.
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
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