How to sum a result of the repeated function in R - r

Question

I have a very complicated function. I need to repeat this function several times and sum the result. This is easy. However, I need to sum them at the same time. Since my function is difficult to show it here, I provide a very simple example just to explain my idea. Please note that (based on the amazing questions from the comments) My function needs to be done pairwise. Also, my matrices are all the same dimensions. Finally, the result is not as a list. I need to assign the result to a new variable. That is,
Res <– myfunc(x[i,j],y[i,j])+myfunc(z[i,j],t[i,j])+..+..
Also, my function must loop over the elements of the matrices. x[i,j].
My matrices are stored in a list.
Mymatrices–list(x,y,z,t).
For example,
x <- matrix(5,5,5)
x[upper.tri(x,diag=T)] <- 0
y <– matrix(4,5,5)
y[upper.tri(y,diag=T)] <- 0
z <- matrix(3,5,5)
z[upper.tri(z,diag=T)] <- 0
t <- matrix(2,5,5)
t[upper.tri(t,diag=T)] <- 0
myfunc <– function(x,y){
sum(x,y)
}
I would like it like this:
Res <– myfunc(x[i,j],y[i,j])+myfunc(z[i,j],t[i,j])+..+..
Suppose I have 10 matrices and would like to have the sum as shown above. It is hard to do it manually. I would like to do this automatically. lapply function takes a list and I do not want it as a list.
Any help, please?

Answer 1

I cant either tell whether you need a matrix in the end or a value. But since you used i,j I presume you need a matrix:
Reduce("+",list(x,y,z,t))
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 14 0 0 0 0
[3,] 14 14 0 0 0
[4,] 14 14 14 0 0
[5,] 14 14 14 14 0
or do you need:
Reduce(sum,list(x,y,z,t))
[1] 140

Answer 2

Let's say your matrices are in a list, paired in the way you want:
input = list(list(x, y), list(z, t))
For convenience, we'll make a version of your function that takes a list as input (we could use do.call or an anonymous function instead, but this is very clear):
myfunc_list = function(x) {
myfunc(x[[1]], x[[2]])
}
We can then sapply the list function to your input list, and sum:
sum(sapply(input, myfunc_list))
# [1] 140

Answer 3

Glad to have helped. To be honest, I'm still not completely sure what you are asking for though - no one thinks your final answer will be a list, just an intermediate step in order to do the summation effectively. Looking at the answers, I think the Reduce function suggested by Onyambu is what you need - where x, y, z, and t are the results from your function (called pairwise on different matrices).
Is the summation really where you need help, or is it efficiently calling your function pairwise on all those matrices? That is a very different question. If that's the case, check out the map2 function in the purrr package. It takes two lists (of the same length) as inputs, computes a function on each element, and returns a list (which can be fed into Reduce).