You can do this:
%sample data
x = [1, 2, 3, 4];
n = length(x);
s = zeros(n, 1); % Initialize s as a vector of zeros
for i = 1:n
s(i) = sum(x(1:i)) % Calculate the sum of the first i elements of x
end
or
s = zeros(n, 1); % Initialize s as a vector of zeros
s(1)=x(1);
for i = 2:n
s(i) = x(i)+s(i-1) % Calculate the sum of the first i elements of x
end
