[R] sum of unknown number of matrices

[Barry Rowlingson]

Shubha Vishwanath Karanth wrote:

> I need:
> 
>> a+b+c+d
> 
>      [,1] [,2]
> 
> [1,]    4   12
> 
> [2,]    8   16
> 
>  
> 
> Something like do.call("+",l) is not working...why is this?

Because do.call constructs a function call with the elements of l as 
arguments, so you end up with:

"+"(1:4, 1:4, 1:4, 1:4)

  but "+" only takes two arguments.

Use 'Reduce':

  > Reduce("+",l)
       [,1] [,2]
  [1,]    4   12
  [2,]    8   16

  Barry