Doubt about xcorr function

Hello!

I have question about the xcorr function.

I have a vector with random bits 0s and 1s.

I do the autocorrelation of this vector and the output is the following:

However, shouldn't the autocorrelation for a random vector trace be like this:

sorry for my paint skills..

What is that space below the plot??? Is there any way to take it out?

Many thanks, João

Answer 1

[Honglei Chen]

You may want to use the 'unbiased' option in xcorr so the normalization is on the number of points used to compute the correlation. In addition, you may want to specify a maxlag because at the edge, there simply are not enough samples to get an accurate estimate. Here is a small example:

[c,l] = xcorr(rand91,1024)>0.5,500,'unbiased')
plot(l,c)

HTH

[Joao]

thanks