[R] Defining functions inside loops

Eduardo de Oliveira Horta eduardo.oliveirahorta at gmail.com
Tue Feb 15 18:23:48 CET 2011 

Yes, that was it. Thanks a lot.

Best regards,

Eduardo

On Tue, Feb 15, 2011 at 2:34 PM, jim holtman <jholtman at gmail.com> wrote:
> The try this:
>
>> s <- c( 0.2, 0.45, 0.38, 0.9)
>> f  <- lapply(1:10, function(i)
> +     local({
> +             local_s <- s[i]
> +             function(x)x^2+local_s
> +           }))
>> rm(s)
>> f[[2]](4)
> [1] 16.45
>>
>
>
>
> On Tue, Feb 15, 2011 at 10:53 AM, Eduardo de Oliveira Horta
> <eduardo.oliveirahorta at gmail.com> wrote:
>> Thanks... but I guess I didn't make myself clear. What I was trying to
>> do was precisely to "store" inside the function the number associated
>> to s[i] rather than the call to s[i], such that I wouldn't need to
>> keep that object in subsequent function calls.
>>
>> In other words, I wanted to use lapply to get functions equivalent to:
>> s <- c( 0.2, 0.45, 0.38, 0.9)
>> f <-list()
>> f[[1]] <- function(x) x^2+0.2
>> f[[2]] <- function(x) x^2+0.45
>> f[[3]] <- function(x) x^2+0.38
>> f[[4]] <- function(x) x^2+0.9
>>
>> Best regards,
>>
>> Eduardo
>>
>>
>> On Tue, Feb 15, 2011 at 7:20 AM, Dennis Murphy <djmuser at gmail.com> wrote:
>>> Hi:
>>>
>>> If you look at the error message, you'll see that you removed s before
>>> evaluating f, and since an element of s is called in the function....
>>>
>>> Try
>>>> s <- c( 0.2, 0.45, 0.38, 0.9)
>>>> f  <- lapply(1:10, function(i)local({ force(i) ; function(x)x^2+s[i]}))
>>>> f[[1]](s)
>>> [1] 0.2400 0.4025 0.3444 1.0100
>>>
>>> f is a list with 10 components, the first of which is
>>> [[1]]
>>> function (x)
>>> x^2 + s[i]
>>> <environment: 0x0000000002a26d48>
>>>
>>> Each component occupies a different environment. To see what you get,
>>>
>>>> f[[1]](0.1)
>>> [1] 0.21
>>>
>>>> for(i in 1:10) print(f[[i]](i))
>>> [1] 1.2
>>> [1] 4.45
>>> [1] 9.38
>>> [1] 16.9
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>>
>>>> for(i in 1:10) print(f[[i]](1))
>>> [1] 1.2
>>> [1] 1.45
>>> [1] 1.38
>>> [1] 1.9
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>> [1] NA
>>>
>>> HTH,
>>> Dennis
>>>
>>> On Mon, Feb 14, 2011 at 9:50 PM, Eduardo de Oliveira Horta
>>> <eduardo.oliveirahorta at gmail.com> wrote:
>>>>
>>>> Hello again.
>>>>
>>>> Let me try something a little more intricate. Let's say instead of
>>>> forcing evaluation of 'i' I'd want to force evaluation of a vector;
>>>> for example:
>>>> s <- c( 0.2, 0.45, 0.38, 0.9)
>>>> f  <- lapply(1:10, function(i)local({ force(i) ; function(x)x^2+s[i]}))
>>>> rm(s)
>>>> f[[1]](0.1)
>>>> Error in f[[1]](0.1) : object 's' not found
>>>>
>>>> Any thoughts?
>>>>
>>>> Best regards,
>>>>
>>>> Eduardo
>>>>
>>>> > sessionInfo()
>>>> R version 2.11.1 (2010-05-31)
>>>> x86_64-pc-mingw32
>>>>
>>>> locale:
>>>> [1] LC_COLLATE=Portuguese_Brazil.1252  LC_CTYPE=Portuguese_Brazil.1252
>>>> [3] LC_MONETARY=Portuguese_Brazil.1252 LC_NUMERIC=C
>>>> [5] LC_TIME=Portuguese_Brazil.1252
>>>>
>>>> attached base packages:
>>>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>>>
>>>> other attached packages:
>>>> [1] Revobase_4.2.0   RevoScaleR_1.1-1 lattice_0.19-13
>>>>
>>>> loaded via a namespace (and not attached):
>>>> [1] grid_2.11.1       pkgXMLBuilder_1.0 revoIpe_1.0       tools_2.11.1
>>>> [5] XML_3.1-0
>>>>
>>>> > On Mon, Nov 15, 2010 at 7:10 PM, William Dunlap <wdunlap at tibco.com>
>>>> > wrote:
>>>> >> You could make f[[i]] be function(t)t^2+i for i in 1:10
>>>> >> with
>>>> >>     f <- lapply(1:10, function(i)local({ force(i) ; function(x)x^2+i}))
>>>> >> After that we get the correct results
>>>> >>    > f[[7]](100:103)
>>>> >>    [1] 10007 10208 10411 10616
>>>> >> but looking at the function doesn't immdiately tell you
>>>> >> what 'i' is in the function
>>>> >>    > f[[7]]
>>>> >>    function (x)
>>>> >>    x^2 + i
>>>> >>    <environment: 0x19d7458>
>>>> >> You can find it in f[[7]]'s environment
>>>> >>    > get("i", envir=environment(f[[7]]))
>>>> >>    [1] 7
>>>> >>
>>>> >> The call to force() in the call to local() is not
>>>> >> necessary in this case, although it can help in
>>>> >> other situations.
>>>> >>
>>>> >> Bill Dunlap
>>>> >> Spotfire, TIBCO Software
>>>> >> wdunlap tibco.com
>>>> >>
>>>> >>> -----Original Message-----
>>>> >>> From: r-help-bounces at r-project.org
>>>> >>> [mailto:r-help-bounces at r-project.org] On Behalf Of Eduardo de
>>>> >>> Oliveira Horta
>>>> >>> Sent: Monday, November 15, 2010 12:50 PM
>>>> >>> To: r-help at r-project.org
>>>> >>> Subject: [R] Defining functions inside loops
>>>> >>>
>>>> >>> Hello,
>>>> >>>
>>>> >>> I was trying to define a set of functions inside a loop, with
>>>> >>> the loop index
>>>> >>> working as a parameter for each function. Below I post a
>>>> >>> simpler example, as
>>>> >>> to illustrate what I was intending:
>>>> >>>
>>>> >>> f<-list()
>>>> >>> for (i in 1:10){
>>>> >>>   f[[i]]<-function(t){
>>>> >>>     f[[i]]<-t^2+i
>>>> >>>   }
>>>> >>> }
>>>> >>> rm(i)
>>>> >>>
>>>> >>> With that, I was expecting that f[[1]] would be a function
>>>> >>> defined by t^2+1,
>>>> >>> f[[2]] by t^2+2 and so on. However, the index i somehow
>>>> >>> doesn't "get in" the
>>>> >>> function definition on each loop, that is, the functions
>>>> >>> f[[1]] through
>>>> >>> f[[10]] are all defined by t^2+i. Thus, if I remove the
>>>> >>> object i from the
>>>> >>> workspace, I get an error when evaluating these functions.
>>>> >>> Otherwise, if
>>>> >>> don't remove the object i, it ends the loop with value equal
>>>> >>> to 10 and then
>>>> >>> f[[1]](t)=f[[2]](t)=...=f[[10]](t)=t^2+10.
>>>> >>>
>>>> >>> I am aware that I could simply put
>>>> >>>
>>>> >>> f<-function(u,i){
>>>> >>>   f<-t^2+i
>>>> >>> }
>>>> >>>
>>>> >>> but that's really not what I want.
>>>> >>>
>>>> >>> Any help would be appreciated. Thanks in advance,
>>>> >>>
>>>> >>> Eduardo Horta
>>>> >>>
>>>> >>>       [[alternative HTML version deleted]]
>>>> >>>
>>>> >>> ______________________________________________
>>>> >>> 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.
>>>> >>>
>>>> >>
>>>> >
>>>>
>>>> ______________________________________________
>>>> 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.
>>>
>>>
>>
>> ______________________________________________
>> 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.
>>
>
>
>
> --
> Jim Holtman
> Data Munger Guru
>
> What is the problem that you are trying to solve?
>

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