[R] Problem with do.call().

[Duncan Murdoch]

On 27/03/2014, 7:38 PM, Thomas Lumley wrote:
> You get what you wanted from
>
> do.call(plot,list(x=quote(x),y=quote(y)))
>
> By the time do.call() gets the arguments it doesn't know how y was
> originally computed, just what values it has.

This works, but it doesn't make sense to me.  The arguments end up with 
the expressions x and y, but why are they evaluated in the right place? 
  Quote doesn't bind an environment to its expressions, does it?  How 
does plot() know where to evaluate them?

Duncan Murdoch


>
>     -thomas
>
>
> On Thu, Mar 27, 2014 at 6:17 PM, Rolf Turner <r.turner at auckland.ac.nz>wrote:
>
>>
>>
>> I was under the impression that
>>
>>          do.call(foo,list(x=x,y=y))
>>
>> should yield the same result as
>>
>>          foo(x,y).
>>
>> However if I do
>>
>>          x <- 1:10
>>          y <- (x-5.5)^2
>>          do.call(plot,list(x=x,y=y))
>>
>> I get the expected plot but with the y-values (surrounded by c()) being
>> printed (vertically) in the left-hand margin of the plot.
>>
>> The help for do.call() says:
>>
>>   The behavior of some functions, such as substitute, will not be the
>>> same for functions evaluated using do.call as if they were evaluated
>>> from the interpreter. The precise semantics are currently undefined and
>>> subject to change.
>>>
>>
>> Am I being bitten by an instance of this phenomenon?  Seems strange.
>>
>> I would be grateful for enlightenment.
>>
>> cheers,
>>
>> Rolf Turner
>>
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>>
>
>
>