%% Cross-Correlation with Multichannel Input
% Generate three 11-sample exponential sequences given by 0.4^n, 0.7^n, and 0.999^n, with n\ge0. Use stem3 to plot the sequences side by side.

N = 11;
n = (0:N-1)';

a = 0.4;
b = 0.7;
c = 0.999;

xabc = [a.^n b.^n c.^n];

stem3(n,1:3,xabc','filled')
ax = gca;
ax.YTick = 1:3;
view(37.5,30)

%
% Compute the autocorrelations and mutual cross-correlations of the sequences. Output the lags so you do not have to keep track of them. Normalize the result so the autocorrelations have unit value at zero lag.

[cr,lgs] = xcorr(xabc,'coeff');

for row = 1:3
    for col = 1:3
        nm = 3*(row-1)+col;
        subplot(3,3,nm)
        stem(lgs,cr(:,nm),'.')
        title(sprintf('c_{%d%d}',row,col))
        ylim([0 1])
    end
end

%
% Restrict the calculation to lags between -5 and 5.

[cr,lgs] = xcorr(xabc,5,'coeff');

for row = 1:3
    for col = 1:3
        nm = 3*(row-1)+col;
        subplot(3,3,nm)
        stem(lgs,cr(:,nm),'.')
        title(sprintf('c_{%d%d}',row,col))
        ylim([0 1])
    end
end

%
% Compute unbiased estimates of the autocorrelations and mutual cross-correlations. By default, the lags run between -(N-1) and N-1.

cu = xcorr(xabc,'unbiased');

for row = 1:3
    for col = 1:3
        nm = 3*(row-1)+col;
        subplot(3,3,nm)
        stem(-(N-1):(N-1),cu(:,nm),'.')
        title(sprintf('c_{%d%d}',row,col))
    end
end

% Copyright 2015 The MathWorks, Inc.