[R] Recursive function for lists

[Thomas Lumley]

On Tue, 11 Jun 2002, John Fox wrote:
>
> I rather like Thomas Lumley's solution, which is simpler than mine, though
> I think that it will be necessary to unlist the result returned by his
> treeapply.
>

Here's an extended version that optionally flattens the result, and has
two ways to control the depth of recursion, using a function IS.LEAF and a
maximum recursion DEPTH.


treeapply<-function (x, FUN,...,IS.LEAF=is.atomic,DEPTH=Inf,FLATTEN=FALSE)
{
    if (DEPTH<=0)
        FUN(x,...)
    else if (IS.LEAF(x))
        FUN(x,...)
    else if (FLATTEN)
        do.call("c",lapply(x, function(n) treeapply(n, FUN,...,IS.LEAF=IS.LEAF,DEPTH=DEPTH-1,FLATTEN=TRUE)))
    else
        lapply(x, function(n) treeapply(n, FUN,...,IS.LEAF=IS.LEAF,DEPTH=DEPTH-1))
}


	-thomas

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