[R] How to convert List object to function arguments?

[hadley wickham]

Have a look at do.call

Hadley

On 3/3/07, Shiazy <shiazy at gmail.com> wrote:
> Dear R gurus,
>
> I have a function "goftests" that receives the following arguments:
> * a vector "x" of data values;
> * a distribution name "dist";
> * the dots list ("...") containing a list a parameters to pass to CDF
> function;
> and calls several goodness-of-fit tests on the given data values against
> the given distribution.
> That is:
>
> ##### BEGIN CODE SNIP #####
>
> # Covert a distribution name to the related CDF function name
> distname2cdfname <- function( dist )
> {
>    if ( dist == "beta" ) { return( "pbeta" ); }
>    if ( dist == "cauchy" ) { return( "pcauchy" ); }
>
>    # many other and personalized (e.g. pareto, ...) distributions ...
>
>    return( "" ); # fall-back case
> }
>
> # Performs some GoF tests (KS, Chi-Square, Anderson-Darling,...)
> # (the "..." list contains parameters for CDF function)
> goftests <- function( x, dist, ... )
> {
>    cdfname <- distname2cdfname( dist );
>    res$ks <- ks.test( x, cdfname, ... );
>    # res$chisq <- ...
>    # res$anddarl <- ...
>
>    return( res )
> };
>
> ##### END CODE SNIP #####
>
> So the problem is passing "..." to CDF function (for instance, see
> ks.test above) in the "right form". The "..." is passed (to "goftests")
> as a list object and it should be converted to an "argument list".
> For instance:
>
> ##### BEGIN CODE SNIP #####
>
> parms <- list( shape1 = 2, shape2 = 5 );
> goftests( x, "beta", parms[["shape1"]], parms[["shape2"]] ); # Works!
> goftests( x, "beta", parms ) # Don't Works!
>
> parms <- list( aNum = 5, aVector = c(1,2,3), aMatrix =
> matrix(c(4,5,6,7,8,9),nrow=2,byrow=T) );
> goftests( x, "my-special-distr", parms[["aVector"]], parms[["aMatrix"]],
> parms[["aNumber"]] ); # Works!
> goftests( x, "my-special-distr", parms ) # Don't Works!
>
> ##### END CODE SNIP #####
>
> Obviously I have to use the "don't work" form.
>
> How can I do this in R (if possible)?
>
> Thank you very much in advance!
>
> Best regards,
>
> -- Marco
>
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