# [R] is there a way to recursilvely lapply

Prof Brian Ripley ripley at stats.ox.ac.uk
Thu Dec 11 21:13:20 CET 2008

```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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

```