For given vector, make a "averaged vector"

For a given 1 by 1000 vector A = (a1 a2 a3 a4 so on,,a1000) and interger n

I want to make vector

   B = (b1 b2 b3 so on,,b(1000-n+1))

with b1 = a1 + a2 + a3 ...+a(n), b2 = a2 + a3 + ....+a(n+1), b(1000-n+1) = a(1000-n+1)+a(1000-n+2)+...a(1000)

Please help me. How can i make such vector B??

Answer 1

[Jan]

b = movsum(a, [0, n], 'Endpoints', 'discard')

Answer 2

[Walter Roberson]

temp = [0, cumsum(A)];
B = temp(n+1:end) - temp(1:end-n);