# [R] Summing functions of lists

Phil Spector spector at stat.berkeley.edu
Sat Nov 13 19:53:09 CET 2010

```Does this version of y do what you want?

y=function(j)sum(sapply(1:3,function(i)x(i,j)))

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

On Sat, 13 Nov 2010, Hiba Baroud wrote:

>
> Hi
>
> I'm trying to sum functions of lists with different lengths. Here is a simplified example of the problem:
>
> r=list(1:3,1:5,1:2)
>
> r
> [[1]]
> [1] 1 2 3
> [[2]]
> [1] 1 2 3 4 5
> [[3]]
> [1] 1 2
>
> x=function(i,j) sum(j*r[[i]])                                # x is a function of two parameters: i & j
>
> y=function(j)                                                     # y is the sum of x over i
> + {
> + s=seq(from=1,to=3,by=1)
> + sum(x(s,j))
> + }
>
> y(1)
> Error in r[[i]] : recursive indexing failed at level 2
>
> The error is clearly due to the lists; I actually tried this code with functions of vectors and scalars and it worked perfectly.
> I tried to use means of summing lists by recursion but it does not work with functions of lists, for e.g.:
>
> y=function(j) x(1,j)
> for(i in 2:3)
> + {
> + y=function(j) y(j)+x(i,j)
> + }
>
> y(1)
> Error: evaluation nested too deeply: infinite recursion / options(expressions=)?
>
> Is there a way to perform this summation?
>
> Thanks!
>
> H.
>
> 	[[alternative HTML version deleted]]
>
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>

```