[R] Dynamic regex/sub changes to function

[William Dunlap]

If you really want to continue to use the function in the supported
package, then you could try asking the maintainer of the package to
make the problematic URL an argument to the function.  I thnk that
changing the function on the fly, no matter how you do it, is likely
to cause problems when the maintainer changes the function in a future
release of the package.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Mon, Sep 22, 2014 at 8:34 AM, Daniel Fuka <drf28 at cornell.edu> wrote:
> Howdy Duncan,
>
> Thanks for the quick reply!  I must be missing something
> simple/obvious. I need to have the "sub()" not return quoted and
> escaped characters to "just edit the language expression". In my
> problem, there is a function that is supported from a different
> package. So I always want to use the supported function as my base...
> but a url in the supported function needs to be changed dynamically
> for my application, which is easiest using "sub()".
>
> I am trying to do what you correctly indicate I would need to do:
> "just edit the language expression that body(fsong) gives you, and
> assign it back"
> BUT, using sub, I get back a quoted string in my example if I just use sed:
>
>> fsong
> function(x){
>  song=paste("my name is fuka,",x)
>  return(song)
> }
> # Using "sub()" becomes:
>> nsong
> function (x)
> {
>     "song = paste(\"my name is muka,\", x)"
>     return(song)
> }
>
> Thanks again for the quick reply and help you are giving me!
> dan
>
> On Mon, Sep 22, 2014 at 10:37 AM, Duncan Murdoch
> <murdoch.duncan at gmail.com> wrote:
>> On 22/09/2014 9:16 AM, Daniel Fuka wrote:
>>>
>>> Howdy,
>>>
>>> I have searched the lists and can not seem to find a solution to my
>>> problem. I need to be able to dynamically modify a string inside a
>>> function to build a new function. "sub" replaces with a quoted
>>> string... and "parse" of "sub" returns expression... How can I get an
>>> unquoted string from a regex to stick into a "body" of a function?
>>
>>
>> It's possible to do what you want, though you don't want to be using
>> parse(), you can just edit the language expression that body(fsong) gives
>> you, and assign it back.  But that's a messy way to solve your problem.
>>
>> Why not create a new function containing the new string?  e.g.
>>
>> makefsong <- function(name = "fuka") {
>>   line1 <- paste("my name is", name)
>>   function(x) {
>>     song <- paste(line1, x)
>>     return(song)
>>   }
>> }
>>
>> f1 <- makefsong()
>> f1("I live on the second floor")
>> f2 <- makefsong("muka")
>> f2("I live on the second floor")
>>
>> Duncan Murdoch
>>
>>>
>>> Thanks for your help!
>>> dan
>>>
>>> # Original Function
>>> fsong=function(x){
>>>   song=paste("my name is fuka,",x)
>>>   return(song)
>>> }
>>> fsong("I live on the second floor")
>>> #
>>> # Copy and modify using "sub" returns quoted string with escaped quotes
>>> #   internally... as expected.. which can not be evaluated.
>>> nsong=fsong
>>> body(nsong)[[grep("fuka",body(nsong))]]=
>>>     sub("fuka","muka",list(body(fsong)[[grep("fuka",body(fsong))]]))
>>>
>>> nsong("I live on the second floor") # broken
>>>
>>> #
>>> # Copy and modify with "parse" of  "sub",  returns expression.. but
>>> without quotes,
>>> # o getting closer.
>>> #
>>> nsong=fsong
>>> body(nsong)[[grep("fuka",body(nsong))]]=
>>>
>>> parse(text=sub("fuka","muka",list(body(fsong)[[grep("fuka",body(fsong))]])))
>>>
>>> ______________________________________________
>>> 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.