# [R] Vectors out of lists?

Phil Spector spector at stat.berkeley.edu
Wed Nov 17 01:24:17 CET 2010

```Eduardo -
Thanks for the reproducible example!
> Y<-list()
> Y[[1]]<-function(u) sqrt(u)
> Y[[2]]<-function(u) sin(u)
> Y[[3]]<-function(u) 1/2*u
> Ybar = function(u)mean(sapply(Y,function(fun)fun(u)))

Since integrate requires a function which accepts a vector
and returns a vector, we'd need to use Vectorize() before
trying to integrate:

> integrate(Vectorize(Ybar),0,1)
0.4587882 with absolute error < 5.6e-05

- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spector at stat.berkeley.edu

On Tue, 16 Nov 2010, Eduardo de Oliveira Horta wrote:

> Thanks, guys... but it seems these suggestions won't work.
>
> Let me try to be more specific with a simple example:
>
> Y<-list()
> Y[[1]]<-function(u) sqrt(u)
> Y[[2]]<-function(u) sin(u)
> Y[[3]]<-function(u) 1/2*u
>
> I wanted something equivalent to
>
> Ybar<-function(u){
>    1/3*(Y[[1]](u) + Y[[2]](u) + Y[[3]](u))
> }
>
> but with arbitrary length(Y) and without using any loops. Also, I can't allow
> for discretization, since I must be able to evaluate Ybar at any u, as I'm
> going to integrate it with the function "integrate".
>
> Thanks again,
>
> Eduardo Horta
>
>
```