plot autocorrelation

Hello guys, might be sort of a beginners question for most of you guys but i am really having trouble tat ploting an autocorrelation function like the example one mentioned in the help section of the function browser "autocorr(econ)"? Any chance somebody could give me a hint on how to plot it alongside with the bounds and label x/y according to the example? many thanks stefan

Answer 1

[Wayne King]

      x = randn(1000,1);         % 1000 Gaussian deviates ~ N(0,1)
      y = filter([1 -1 1],1,x);  % Create an MA(2) process
      [acf,lags,bounds] = autocorr(y);
      stem(lags,acf); xlabel('Lag'); ylabel('\rho(k)');
      hold on;
      h = line(lags,bounds(1)*ones(length(acf),1));
      h1 = line(lags,bounds(2)*ones(length(acf),1));
      set(h,'color',[1 0 0]);
      set(h1,'color',[1 0 0]);

[stefan strasser]

Thank you very much Wayne! This was of big help!

[Kevin Holst]

Make sure you click 'Accept Answer' so the helpers on here know you've got what you needed.

[Bill Tubbs]

Note: 'autocorr' requires Econometrics Toolbox.

Answer 2

[Yashwanth]

%ECE24063
clc;
clear;
close all;

% Parameters
Am = 5;
fm = 2e3;
fc = 10 * fm;

t = 0:1e-6:2e-3;

% Message signal
m = Am * cos(2*pi*fm*t);

% Modulation index values
beta_values = [0.5, 2, 10];

figure;

for i = 1:length(beta_values)
    beta = beta_values(i);
    
    % Frequency Modulated Signal
    s = cos(2*pi*fc*t + beta * sin(2*pi*fm*t));
    
    subplot(3,1,i);
    plot(t, s);
    title(['FM Signal for \beta = ', num2str(beta)]);
    xlabel('Time');
    ylabel('Amplitude');
end