[R] how to manipulate ... in the argument list

[Witold E Wolski]

Duncan suggested to use the argument explicitly and combine it with
the missing function which is for this problem also my preferred
solution:


image.2 <- function(x, col , breaks, ...){
  # function is manipulating colors (adding a few)
  # since it changes colors it needs to update breaks if defined.

  if( !missing(breaks) ){
     #manipulate breaks

    image(x, col, breaks  ,...)

   }else{
      image(x,col ,...)
   }
}

It is good to know that I also could have used do.call.

I also learned yesterday that it is better to search for dot dot dot
argument or for elipsis instead of  ...

best





On 11 May 2016 at 15:45, Vito M. R. Muggeo <vito.muggeo at unipa.it> wrote:
> Hi Witold,
> use do.call()
>
> list.args<-list(...)
>
> #modify 'list.args' (add/delete/modify)
>
> do.call(image, list.args)
>
> best,
> vito
>
>
> Il 11/05/2016 10.45, Witold E Wolski ha scritto:
>>
>> Hi,
>>
>> I am looking for a documentation describing how to manipulate the
>> "..." . Searching R-intro.html gives to many not relevant hits for
>> "..."
>>
>> What I want to do is something like this :
>>
>>
>> image.2 <- function(x, col , ...){
>>   # function is manipulating colors (adding a few)
>>   # since it changes colors it needs to update breaks if defined.
>>
>>    breaks <- list(...)$breaks
>>
>>   if( !is.null( list(...)$breaks ) ){
>>      #manipulate breaks
>>
>>     image(x, col, breaks = breaks ,...)
>>
>>    }else{
>>       image(x,col ,...)
>>    }
>> }
>>
>> but in order to get it working I will need to remove breaks from ...
>> since otherwise I am getting multiple defined argument for breaks.
>>
>> So how to manipulate the "..." argument? Or should I use a different
>> pattern
>>
>> best
>>
>>
>>
>
> --
> ==============================================
> Vito M.R. Muggeo
> Dip.to Sc Statist e Matem `Vianelli'
> Università di Palermo
> viale delle Scienze, edificio 13
> 90128 Palermo - ITALY
> tel: 091 23895240
> fax: 091 485726
> http://dssm.unipa.it/vmuggeo
> Associate Editor, Statistical Modelling
> ===============================================



-- 
Witold Eryk Wolski