Pier-Yves Lessard
  • Member for 5 years, 7 months
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4 answers
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4k views
$\tt fft$ vs. $\tt fftshift$ in MATLAB: Please explain
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6 votes

I believe you simply misunderstand what these functions are supposed to do. You get different results because they are not meant to do the same thing. I think it would be relevant that you read the ...

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2 answers
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8k views
Plotting the magnitude response of a filter?
4 votes

If you want to code your own application that plot the magnitude response, you first need to extract the poles and zeros from your transfer function in the $Z$ domain. The process that follows can ...

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1 answers
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173 views
Weird results when using MATLAB's $\tt butter$ function?
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4 votes

The answer to your question can mainly be found in the Matlab documentation. The butter function can design filters either in the analog domain as well as in the discrete domain. In order to make an ...

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2 answers
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135 views
Can I compute Fourier series without looping through all frequencies?
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3 votes

Make sure you do not mix up FFT and DFT, they gives identical results, but are different. DFT complexity is about $O(N^2)$ while FFT complexity is $\frac{34}{9}N\log_2(N)$. This makes a huge ...

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1 answers
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324 views
The transform function of a digital FIR filter
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2 votes

First, we call $H(z)$ the transfer function (not transform). Next, I believe you should have a look at Wikipedia first, many of your questions shows no preliminary research. Still, I'll try to ...

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3 answers
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8k views
Understanding overlapping in STFT
2 votes

Your overlap is computed right here, in the hop_size variable. hop_size = np.int32(np.floor(fft_size * (1-overlap_fac))) Let's make a small example. You use a 1024 sample fft to compute the STFT of ...

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1 answers
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293 views
Updating FFT algorithm accordingly when upsampling/resampling
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2 votes

Your whole problem is due to the fact that you have made a wrong assumption. Increasing the sample rate does not increase the frequency resolution. It will increase the Nyquist frequency (the highest ...

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4 answers
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11k views
Do we use closed loop or open loop information in Bode plot, Nyquist plot and Root Locus?
2 votes

It looks like you are considering these analysis like part of a universal streamline desing process. These analysis techniques are simply tools that helps you understand the behaviour of your system, ...

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2 answers
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477 views
Determine filter type (HPF or LPF) by its coefficients
1 votes

I am not sure if my answer will correctly suits your question as it seems a little confusing. Anyway, I understand that you want to eliminate the initial transition of your filter. What I propose is ...

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1 answers
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194 views
temporal high-pass filtering to approximate phase derivative
1 votes

I am not familiar with the algorithm you have proposed, but I believe I can answer the question you asked. Once you have computed the DFT of your image, what you get is a 2D array of complex number. ...

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2 answers
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157 views
Estimate mean amplitude in frequency range using fft
1 votes

The Discrete Fourier Transform is a summation : $$ X_k =\sum_{n=0}^{N-1}x_ne^{-j2\pi kn/N} $$ Which means, the more data you have, the bigger the output mangitude. What you can do is normalizing ...

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2 answers
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52 views
How to discover the caracteristic frequency of the use of an app by someone
1 votes

If I had to solve your problem, I would do as FAT32 suggested an go with a statistical approach before using the FFT. Here is what I would propose that might give you more meaningful insights on the ...

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2 answers
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3k views
How to design digital filter from transfer function
1 votes

Following OP comment requesting more details to Maximilian Matthé's answer: Just like mentioned, the key to your question is the Bilinear Transform, where you substitute $s$ (or $j\omega$ in your ...

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3 answers
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5k views
How can I plot the spectrum of a signal in MATLAB?
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1 votes

In order to plot the amplitude of a spectrum in matlab, here's what you can do. Where y is the signal fs is the samplig frquency Code: spectrum = 10*log(abs(fftshift(fft(y))) / length(y)); %...

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1 answers
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111 views
How to compare multiple polynomials in MATLAB?
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0 votes

Based on what you share, this is the best answer I can give. I see two methods: Method #1, Instead of making N polynomials (if N is the number of ribs), you could fit a curve for all the ribs at ...

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