dft Questions
3
Solved
I am new to digital signal processing. I have the following sensor sample data
Time(milliseconds) data
------------------ -------------------
0 0.30865225195884705
60 0.14355185627937317
100 -0....
Sartorial asked 7/12, 2015 at 12:34
2
Solved
I need to perform FFT and Inverse-FFT transformations. The input would be vector and matrices of double. Ideally, the output should be an array of std::complex but I can live with double _Complex. ...
3
Solved
When using librosa.stft() to calculate a spectrogram, how does one get back the associated frequency values? I am not interested in generating an image as in librosa.display.specshow, but rather I ...
Rocker asked 11/8, 2020 at 2:1
7
Solved
1
Solved
I am trying to solve the 1D heat equation using a complex to complex IDFT. The problem is that the output after a single timestep does not seem to be correct. I have included a simple example below...
2
Solved
Can I expect a speedup when using FFTW (http://www.fftw.org/) instead of OpenCV's cvDFT (http://goo.gl/YCHj0)?
My program's runtime is heavily determined by the application of inverse and forward ...
4
Solved
I'm currently learning about discret Fourier transform and I'm playing with numpy to understand it better.
I tried to plot a "sin x sin x sin" signal and obtained a clean FFT with 4 non-zero point...
Retroflexion asked 2/9, 2014 at 13:26
2
i have a time discrete signal that may contain many missing values. and i want to do a fourier transformation on it.
what can i do to handle them properly?
following diagram may show the case
si...
3
Solved
I'm new to all of this, I would like to get a magnitude spectrum from an image and then rebuild the image from a modified magnitude spectrum.. But for now i'am getting a very dark reconstitution.
...
1
Solved
I am trying to understand how the fft and ifft functions work in python. I made a simple example of an imaginary odd function to compute the inverse Fourier transform in the hopes of getting a real...
Arbitration asked 4/3, 2019 at 3:53
1
Solved
I have been fighting with a very weird bug for almost a month. Asking you guys is my last hope. I wrote a program in C that integrates the 2d Cahn–Hilliard equation using the Implicit Euler (IE) sc...
1
I would like to implement multiplication of polynomials using NTT. I followed Number-theoretic transform (integer DFT) and it seems to work.
Now I would like to implement multiplication of polynom...
Diazole asked 11/9, 2018 at 6:57
3
Solved
I need to multiply two polynomials each having small integral coefficients. I need a fast FFT routine in C/C++ which can convolve them. I have seen several libraries but they seem to be too large s...
Calycle asked 10/3, 2011 at 4:30
2
Solved
I'm trying to solve a problem with python+numpy in which I've some functions of type that I need to convolve with another function . In order to optimize code, I performed the fft of f and g, I mul...
2
Solved
I have a problem with FFT implementation in Python. I have completely strange results.
Ok so, I want to open image, get value of every pixel in RGB, then I need to use fft on it, and convert to im...
3
Solved
I am trying to do discrete Fourier transforms in C.
Initially just the brute-force method. First I had the program open a data file (of amplitudes) and put the data into an array (just one, since ...
2
Solved
I have begun (a small project) to calculate the power spectrum of an image in the frequency domain.
So, what I have till now is the following:
%// close all; clear all; %// not generally apprecia...
Intort asked 9/12, 2013 at 22:24
4
Solved
I am having a hard time understanding what should be a simple concept. I have constructed a vector in MATLAB that is real and symmetric. When I take the FFT in MATLAB, the result has a significant ...
Hawsepiece asked 30/7, 2014 at 16:43
1
Solved
i want to change the phase of a signal in the frequency domain. so i generated a cosine test signal to verify the code:
ycheck = cos(2*pi*t);
when i want to shift the phase about pi/4 i perform ...
Brynhild asked 15/9, 2015 at 11:5
1
Solved
I am currently trying to implement fft into avr32 micro controllers for signal processing purposes using kiss fft.
And having a strange problem with my output.
Basically, I am passing ADC samples...
Stannary asked 29/5, 2015 at 0:1
1
Solved
I want to make a 3d plot of 2d plots of function y
where y is the dft of function z with having as axis k(x) w0(y) and amplitude(y)(z), where k is the dft variable in frequency domain and w0 is a ...
1
Solved
I've been trying to find some places to help me better understand DFT and how to compute it but to no avail. So I need help understanding DFT and it's computation of complex numbers.
Basically, I...
Dynamiter asked 14/10, 2014 at 5:6
1
Solved
I have data for Velocity vs time. The time steps are not uniform, but the Velocity data is a wave. How do I calculate the principal frequency of the velocity using FFT of Python? Most of the exampl...
2
Solved
This is probably a very naive question but here it is.
I want to calculate Fourier transform of a function f(x). So I define a numpy array X and pass through vectorized function f. Now if I calcul...
Athenaathenaeum asked 16/5, 2014 at 17:7
1
Solved
I try to validate my understanding of Numpy's FFT with an example: the Fourier transform of exp(-pi*t^2) should be exp(-pi*f^2) when no scaling is applied on the direct transform.
However, I find...
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