assign attributes to a function on the fly

Question

I am trying to use function A within function B. I want to fix the attributes of function A dependent on the input from function B. As a simple example:

somfun<-function(x,atra){

   functionA(x,atra$subset)

}

Sorry if it is vague. But I need atra to operate as the arguments like paste(x,sep='sss') etc. but with an arbitrary number of arguments. `atra would be a named vector for example or whatever was appropriate.

example

atra<-list(a=1:2,b=3:4,c=5:6,1:2,sep='')

x<-'data'
somfun<-function(x,atra){

   c(atra[[1]],atra[[2]],atra[[3]],paste(x,atra[[5]]))

}

but i want all the names to preserve and paste to realise that atra[[5]] is saying sep=''

Use the ellipsis, `...`, see: http://stackoverflow.com/q/3057341/269476 — James, Aug 31 '12 at 13:54
atra would be a list or vector of arbitrary length also its names etc would be dynamic. — user1609452, Aug 31 '12 at 14:01
It would be beneficial to give an actual concrete example of what you want to do. — Dason, Aug 31 '12 at 14:16
Do you mean `atra` rather than `atr` in the second to last line in that example? — David Robinson, Aug 31 '12 at 14:25
And atra[4] *isn't* `sep=''`, it's `b2="4"` (try it: `c(a=1:2,b=3:4,c=5:6,1:2,sep='')[4]`). The `sep` argument is `atra[9]`. — David Robinson, Aug 31 '12 at 14:28

score 2 · Accepted Answer · answered Aug 31 '12 at 14:44

2

You want the do.call function, which can call a function using a list (including named arguments). For example:

do.call(paste, list("hello", "world", sep="/"))
# [1] "hello/world"

answered Aug 31 '12 at 14:44

David Robinson

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yes thats it `aa<-list(a=1:2,b=3,collapse=',')` `do.call(paste,aa)` for example. thanks alot – user1609452 Aug 31 '12 at 14:48

assign attributes to a function on the fly

1 Answers1