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Top 12 Matlab projects from matlabsolutions.com

Looking for inspiring MATLAB projects to sharpen your skills or impress in your next assignment? At MATLABSolutions.com , we’ve curated the top 12 MATLAB projects that showcase the power of MATLAB in signal processing, image analysis, machine learning, and more. These hands-on examples, complete with code and explanations, are perfect for beginners and advanced users alike. Dive in and explore the best MATLAB projects to elevate your expertise! Signal Smoothing with Moving Average Filter Master signal processing by smoothing noisy data using MATLAB’s movmean function. This project cleans a synthetic sine wave, teaching you noise reduction basics. Ideal for audio or sensor data analysis. Get the code at MATLABSolutions Projects Image Edge Detection Using Canny Filter Explore image processing with MATLAB’s Canny edge detection algorithm. This project highlights edges in any photo, perfect for computer vision applications. Download the script and try it on your own images! Bitcoin Price ...

Why is noise required to get expected Magnitude Squared Coherence (mscohere)

 I am missing something with magnitude Squared Coherence and/or its algorithm. If two signals are compared without or with little noise I get unexpected results. As an example taking from the ML help page:

 
Fs = 1000; t = 0:1/Fs:1-1/Fs;
 
x = cos(2*pi*100*t)+sin(2*pi*200*t)+0.5*randn(size(t)); y = 0.5*cos(2*pi*100*t-pi/4)+0.35*sin(2*pi*200*t-pi/2)+ ... 0.5*randn(size(t)); [Pxy,F] = mscohere(x,y,hamming(100),80,100,Fs);
 
gives the expected two peak response. I would have thought that with no noise the mscohere would be similar and even stronger but it is not. Run the same  code without the noise
 
x = cos(2*pi*100*t)+sin(2*pi*200*t); y = 0.5*cos(2*pi*100*t-pi/4)+0.35*sin(2*pi*200*t-pi/2);
 
[Pxy,F] = mscohere(x,y,hamming(100),80,100,Fs);
 
and rather than getting two strong peaks and the rest near or at zero, you get unity for all frequencies.
 
You don't need much noise, 0.5% or -46dB will do. Below this and the results get real funky.
 
Furthermore, without some noise the algorithm sees harmonics very strongly even though they are not in both signals:
 
x = cos(2*pi*100*t)+sin(2*pi*200*t)+0.5*randn(size(t)); y = 0.5*cos(2*pi*100*t-pi/4);
 
still gives two strong peaks at 100 and 200 unless y has noise. Then all is as expected.

ANSWER



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You might be thinking of CPSD instead of MSCOHERE. MSCOHERE will normalize CPSD by the PSD of each signal (i.e. Cxy = (abs(Pxy).^2)./(Pxx.*Pyy), where Pxy is the CPSD. When the spectrum of Pxy, Pxx and Pyy are very near zero, you'll be looking at division of two numbers very close to zero. Adding the noise decouples them somewhat.

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Top 12 Matlab projects from matlabsolutions.com

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