Summing elements of a vector without a for loop

Given a vector/array v of length , I would like to create a new vector of length M where the 1st component is the sum of the 1st 5 elements of v, the 2nd element is the sum of the next 5 elements of v,... and so on until we get to the last element which is the sum of the last 5 elements of v.

Is there a quick way to do this without using a for loop?

Answer 1

[Yongjian Feng]

How about this:

M=3; % you know your M

v = ones(1, M^2); % your v vector
vReshaped = reshape(v, M, M)'; % Note need this.
result = sum(vReshaped, 2)';

[Yongjian Feng]

Hm.. I made a mistake above. It should be this:

M = 3;
v = [1:9]

vReshaped = reshape(v, M, M)'; % need to transpose it!
result = sum(vReshaped, 2)';

[Stephen23]

n = 3;
v = 1:9; % square brackets are not required
r = sum(reshape(v,n,n),1) % transpose is not required

r = 1×3

6 15 24

[Yongjian Feng]

Cool. Even better.

Answer 2

[KSSV]

Read about movsum

https://in.mathworks.com/help/matlab/ref/movsum.html