R - ff package - arithmetic operations on matrices

Question

Is there a way to do simple arithmetic operations on ff class matrices? ie something like this:

> library(ff)
> a = ff(1, vmode = "double", dim = c(3,4))
> b = ff(2, vmode = "double", dim = c(3,4))
> a+b
Error in a + b : non-numeric argument to binary operator

I know ffbase can do this on vectors, but haven't found anything for matrices. Thanks.

Answer 1

Reading ?LimWarn I see a details section entitled "Multiple vector interpretation in arrays" whose penultimate sentence is:

To access the array elements in R standard dimorder you simply use [ which dispatches to [.ff_array.

a[]+b[]
     [,1] [,2] [,3] [,4]
[1,]    3    3    3    3
[2,]    3    3    3    3
[3,]    3    3    3    3

(The results is an not an ff -object.)

Or, as hinted at in ?ff :

as.ram(a) +as.ram(b)
     [,1] [,2] [,3] [,4]
[1,]    3    3    3    3
[2,]    3    3    3    3
[3,]    3    3    3    3
attr(,"physical")
(hidden, use physical(x) to access the physical attributes and vmode(x) for accessing vmode)
attr(,"virtual")
(hidden, use virtual(x) to access the virtual attributes)
attr(,"vmode")
[1] "double"

(The result is an ff -object.)