I am trying to write a code for the colculate autocorrelation function. Could you suggest what I'm doing wrong. Thanks in advance
i = 1:199;
U =sin(0.3*i);
sum_1 = 0;
for tau = 1:length(U)
for t = tau:length(U)-1
sum_1 = sum_1+sum(U(t).*U(t+1-tau));
r(tau)=sum_1;
end
end
You can do something like this. This is an implementation of the original algorithm with only a small optimization; calculating half the sequence and copying the remaining half.
n = length(x);
m = 2*n - 1;
rxx = zeros(1,m);
for i = 1:length(x)
rxx(i) = dot(x(n-i+1:n), x(1:i).');
rxx(m-i+1) = rxx(i)';
end
Example:
x = [2, 3, -1];
rxx =
-2 3 14 3 -2
% MATLAB built-in
xcorr(x,x)
ans =
-2 3 14 3 -2