[R] use list as function arguments

[Greg Snow]

?do.call

On Thu, May 24, 2012 at 9:32 AM, Alexander Shenkin <ashenkin at ufl.edu> wrote:
> Hello Folks,
>
> Is there any way to pass a list into a function such that the function
> will use the list as its arguments?  I haven't been able to figure that out.
>
> The background: I'm trying to build a function that will apply another
> function multiple times, each time with a different set of specified
> arguments.  I'm trying to figure out how to pass in a list of argument
> lists, then loop through the top-level list, passing in the lower-level
> list as function arguments.
>
> pseudocode:
>
> b = list( list( arg1 = 1, arg2 = 2 ),
>          list( arg1 = 3, arg2 = 4 )
>        )
>
> a <- apply_function(arglist) {
>        for (i in length(arglist)) {
>                b(arglist[i])
>        }
> }
>
>
> Specifically, the actual use I'm trying to implement is a function to
> format columns of data frames and matrices independently.  What I have
> so far is below, but it's not working.  Perhaps I'm going about this the
> wrong way?
>
>
> format_cols <- function(x, format_list = list()) {
>    # usage: length(format_list) must equal ncol(x)
>    #        format list should be a list of lists of key=value pairs
> corresponding to format settings for each column
>
>    if (is.data.frame(x)) {
>        newout = data.frame()
>    } else if (is.matrix(x)) {
>        newout = matrix()
>    }
>
>    for (i in 1:ncol(x)){
>        newout = cbind(newout, format(x,format_list[[i]]))
>        x[,i] = format(x,format_list[[i]])
>    }
>    return(newout)
> }
>
> Thanks,
> Allie
>
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-- 
Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com