How can I get the sum of every 3 elements of array?

Hallo, how can I get the sum of every 3 elements of an large array in an efficient way without using a for loop?

%
%I have an array with 30 elements
A = [11:40]
%
%What I want is an array B with 10 elements
B(1) = sum(A(1:3))
B(2) = sum(A(4:6))
B(3) = sum(A(7:9))
B(4) = sum(A(10:12))
%....
%with the result
B
%B = [36    45    54    63 ....
%...

How can I do this in an efficient way?

Answer 1

[BhaTTa]

Hey @John Go, you can achieve it by using 'reshape' function. The idea is to reshape your array into a matrix where each column contains the elements you want to sum, and then use the sum function to compute the sums along the columns

Below I have attched the code for the same:

% Define the array
A = 11:40;

% Reshape the array into a 3-row matrix
% Each column will have 3 elements from A
reshapedA = reshape(A, 3, []);

% Sum along each column
B = sum(reshapedA, 1);

% Display the result
disp('B =');
disp(B);

Hope it helps.