[R] is there a way to recursilvely lapply

[Prof Brian Ripley]

On Thu, 11 Dec 2008, Whit Armstrong wrote:

> for a simple example:
>
> x <- list()
> x[["a"]] <- list(a=c(1,2,3),b=c(3,4,5))
> x[["b"]] <- list(a=c(6,7,8),b=c(9,10,11))
>
> lapply(x,sum)
>
>
> this fails w/
> Error in FUN(X[[1L]], ...) : invalid 'type' (list) of argument
>
> Just wondering if I have overlooked something obvious.

rapply?  Which is linked from ?lapply (I just checked).  Perhaps

> rapply(x, sum)
a.a a.b b.a b.b
   6  12  21  30

or

> rapply(x, sum, how="list")
$a
$a$a
[1] 6
.....

>
> one can also do:
>
> lapply(x,lapply,sum)
>
> but that assumes that you already know how many levels you have, and
> that all the levels are consistent.
>
> -Whit
>
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> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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