how to plot auto correlation and cross correlation function in a single figure?

while plotting the ACf and CCF i didnt get the negative side of Auto correlation fucntion. I am getting only positive side only.

x=sin(2*pi*f/fs*t);

y=cos(2*pi*f/fs*t);

[ACF,Lags,Bounds] = autocorr(x,nLags,nSTDs);

[XCF,Lag,Bound] = crosscorr(x,y,nLags,nSTDs);

plot(Lags,ACF);

hold on

plot(Lag,XCF);

grid on

i getting output like given figure. Help me to get the negative side of the ACF.

[Adam]

Did you read the help for autocorr?

'The elements of acf correspond to lags 0,1,2,...,numLags. The first element, which corresponds to lag 0, is unity (i.e., acf(1) = 1).'

[vinod kumar govindu]

what we have to do for getting response at negative lags also? I am new to the matlab and dsp.

Answer 1

[David J. Mack]

The negative autocorrelation is the same as the positive as you use the same signal for the correlation. So if you want to pretend there is a negative part:

plot([-Lags(end:-1:1) Lags],[ACF(end:-1:1) ACF]);

Greetings, David