[R] how to use "..."

[Patrick Burns]

There is now a blog post that attempts to
answer the question in the subject line:

http://www.burns-stat.com/the-three-dots-construct-in-r/

Pat

On 17/01/2013 14:36, Ivan Calandra wrote:
> Dear users,
>
> I'm trying to learn how to use the "...".
>
> I have written a function (simplified here) that uses doBy::summaryBy():
> # 'dat' is a data.frame from which the aggregation is computed
> # 'vec_cat' is a integer vector defining which columns of the data.frame
> should be use on the right side of the formula
> # 'stat_fun' is the function that will be run to aggregate
> stat.group <- function(dat, vec_cat, stat_fun){
>      require(doBy)
>      df <-
> summaryBy(as.formula(paste0(".~",paste0(names(dat)[vec_cat],collapse="+"))),
> data=dat, FUN=stat_fun)
>      return(df)
> }
>
> Example, works fine:
> my_data <- structure(list(cat = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 2L,
> 2L, 2L, 2L), .Label = c("A", "B"), class = "factor"), varnum =
> c(-0.754816565434373,
> -1.94101630973709, -0.102461836059522, -0.519952759645808,
> -1.73772800855664,
> -1.13939178585609, 0.522356715260142, -0.701428514907824, 1.45197576541159,
> 0.0844567413828095)), .Names = c("cat", "varnum"), row.names = c(NA,
> -10L), class = "data.frame")
> stat.group(dat=my_data, vec_cat=1, stat_fun=mean)
>
>
> Now summaryBy() has an "..." argument and I would like to use it.
> For example, I would like to be able to add the trim argument to my call
> like this:
> stat.group(dat=my_data, vec_cat=1, stat_fun=mean, trim=0.2)
>
>
> I know I can do it using this "..." but I have no idea how to do it.
> I've tried to search for it, but a search with "..." doesn't yield
> interesting results!
>
>
> Thank you in advance for your help!
> Ivan
>

-- 
Patrick Burns
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twitter: @burnsstat @portfolioprobe
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