[R] Evaluation of variable assigned to a function name
Uwe Ligges
ligges at statistik.tu-dortmund.de
Mon Jan 10 19:14:00 CET 2011
On 10.01.2011 18:24, carol white wrote:
> If it doesn't make sense, how to invoke in the bar function, my.func with
> specified parameters with known values and how to invoke my.func.user if the
> user defines his own function (without specifying the parameters)?
he arguments must be specified in arglist, of course.
I guess you want something completely different, hence it might make
sense to explain what you really intend to do and what your code is so far.
Uwe Ligges
>
>
> ----- 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 6:10:58 PM
> Subject: Re: [R] Evaluation of variable assigned to a function name
>
>
>
> 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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