What is the purpose of this code?

Question

Michael 2023-2-20

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https://ww2.mathworks.cn/matlabcentral/answers/1915730-what-is-the-purpose-of-this-code

回答： Luca Ferro 2023-2-21

What is the purpose of this code? Sorry, I do not have the function for signal, but I hope the code is enpugh for you to answer the question.

a) Plot the correlation between the signal and 100 different sine waves.

b) Plot the crosscorrelation between the signal and 100 different sine waves.

c) Plot the autocorrelation between the signal and 100 different sine waves.

d) Plot the covariance between the signal and 100 different sine waves.

e) Plot the crossvariance between the signal and 100 different sine waves.

clear all;
close all;
clc;
% What is the purpose of this code?
load signal;
fs = 100;
t = (1:length(signal))/fs;
for i = 1:100
    f(i) = 0.35*i;
    x = sin(2*pi*f(i)*t);
    rxy = xcorr(signal,x);
    rmax(i) = max(rxy);
end
plot(f,rmax,'k');

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the cyclist 2023-2-20

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Answer 1

Luca Ferro 2023-2-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1915730-what-is-the-purpose-of-this-code#answer_1176190

line per line

load signal; %load signal

fs = 100;

t = (1:length(signal))/fs; %create linspace (the time axis)

for i = 1:100 %cycle 100 times

f(i) = 0.35*i; %constant which changes value linearly every cycle, see below

x = sin(2*pi*f(i)*t); %generates a different sine wave at every cycle, the difference is guaranteed by f

rxy = xcorr(signal,x); %calculates the correlation between signal and x (it's an array), x is the sine generated in the current cycle

rmax(i) = max(rxy); %stores the maximum value of the above calculated array in a second array

end

plot(f,rmax,'k'); %plots every maximum correlation value stored

basically every cycle it creates a sine wave, compares it to the given signal, finds the maximum correlation, stores it. Once the cycle is done it plots it.