Dear all,
I am was not convinced or may be could not understand the correlation in matlab i.e. xcorr function. So to test I simple made two exactly similar sine wave without any delay, and it gives me delay of 21. I cannot understand why. please first see the code below
if true
fo=200; fs=2500;
t=0:1/fs:.008;
x=sin(2*pi*fo*t);
y=x;
%correlation start here xc = xcorr(x,y); [a,delay]=max(xc); subplot(3,1,1); plot(t,x); %xlabel(t); subplot(3,1,2); plot(t,y); subplot(3,1,3); plot(xc);
display(sprintf('maximum of xc is %d',max(xc))); display(sprintf('delay is %d',delay)); end
So I get the delay at the index 21, where I think we should not have any delay. Note that the x and y both have 21 elements. What I understand is, may be matlab implicitly padd zeros to the second element, in this case y,
Also the please clarify one more thing that the maximim value in the vector 'xc' indicates that at this point the peaks of the two points come together right...!
Also please note that in the detail help of xcorr it is mentioned that...
In all cases, the cross-correlation or autocorrelation computed by xcorr has the zeroth lag in the middle of the sequence, at element or row maxlags+1 (element or row N if maxlags is not specified).
What does that mean. How in the world can I find the delay between my two signals, please suggest since I have tried many things but cannot get certain answer.
Thanks in advance, Jaffry
