How to use vectorization to sum every five elements in 100x1 vector?

I have tried this code..

c = (1:100)'; % Dummy data

for n = 1:20    % This one works
    m(n) = 1 + (n - 1)*5;
    p(n) = 5 + (n - 1)*5;
    csum(n,:) = sum(c((m(n):p(n)),:));
end

nn = 1:20;  % The vectorization code adds only the first five elements.
mm(nn) = 1 + (nn-1)*5;
pp(nn) = 5 + (nn-1)*5;
ccsum(nn,:) = sum(c((m(nn):p(nn)),:));

The result that I want is the one like csum but for vectorization's result, ccsum is only at the sum of the first five elements in c. Please help..

Answer 1

[Walter Roberson]

csum = sum( reshape(c, 5, []) ).' ;

[mrbond99]

Thank you, Walter