fft Questions
2
I am willing to apply Fourier transform on a time series data to convert data into frequency domain. I am not sure if the method I've used to apply Fourier Transform is correct or not? Following is...
Utta asked 5/11, 2018 at 17:14
7
I am taking a jpg image and using numpy's fft2 to create/save a new image. However it throws this error
"IOError: cannot write mode F as JPEG"
Is there an issue with CMYK and JPEG files in PIL...
Goat asked 23/5, 2013 at 17:52
3
Solved
I want numerically compute the FFT on a numpy array Y. For testing, I'm using the Gaussian function Y = exp(-x^2). The (symbolic) Fourier Transform is Y' = constant * exp(-k^2/4).
import numpy
X ...
3
Solved
So, I am probably missing something obvious, but I have searched through lots of tutorials and documentation and can't seem to find a straight answer. How do you find the frequency axis of a functi...
5
There isn't single one working example on whole internet of how to perform FFT analysis of a sound file/buffer/audiobuffer in browser without need for playback. Web audio API has been changed too m...
Epigynous asked 16/2, 2019 at 18:34
2
Solved
I have image of skin colour with repetitive pattern (Horizontal White Lines) generated by a scanner that uses a line of sensors to perceive the photo.
My Question is how to denoise the image ef...
Shena asked 28/12, 2020 at 15:41
2
Solved
I am trying to perform a FFT on a song (audio file in wav format, about 3 minutes long) which I created as follows, just in case it is relevant.
ffmpeg -i "$1" -vn -ab 128k -ar 44100 -y -ac 1 "${1...
Rani asked 26/12, 2017 at 19:15
2
Solved
I want to Fourier transform a function psi(x), multiply it by a k-space function exp(-kx^2-ky^2), and then inverse Fourier transform the product back to x-space.
But my x-space and k-space grids ...
2
Solved
I've got a time series of sunspot numbers, where the mean number of sunspots is counted per month, and I'm trying to use a Fourier Transform to convert from the time domain to the frequency domain....
11
Solved
Is there any general-purpose form of short-time Fourier transform with corresponding inverse transform built into SciPy or NumPy or whatever?
There's the pyplot specgram function in matplotlib, wh...
Hennahane asked 17/3, 2010 at 1:12
4
I'm writing some code to recover the rotation, scaling and translation of a test image relative to a template using phase correlation, a la Reddy & Chatterji 1996. I take the FFT of my original...
Aniseikonia asked 6/12, 2012 at 13:2
4
Solved
I'm trying to implement a Fast Fourier Transform (Radix-2) in MS's Excel VBA. The code I'm using pulls data from a range in the worksheet, does the calculations, then dumps the results in the adjac...
Memoried asked 11/4, 2016 at 14:55
1
I checked all the answers on stackoverflow regarding this topic, but any solution does not work with my dataset.
The dataset consists of 600 amplitudes sampled at 60 samples per second.
In this dat...
Segal asked 17/12, 2022 at 17:57
8
Solved
All the FFT implementations we have come across result in complex values (with real and imaginary parts), even if the input to the algorithm was a discrete set of real numbers (integers).
Is it no...
Gherardo asked 24/4, 2012 at 19:15
7
In the book "Computational Fourier Optics, A Matlab Tutorial" by David Voelz, it is written that a call to fftshift is needed before a call to fft or ifft, but in the MATLAB documentation...
10
Solved
I can write something myself by finding zero-crossings of the first derivative or something, but it seems like a common-enough function to be included in standard libraries. Anyone know of one?
My...
Virtuosic asked 11/11, 2009 at 5:54
2
Solved
I analyzed the sunspots.dat data (below) using fft which is a classic example in this area. I obtained results from fft in real and imaginery parts. Then I tried to use these coefficients (first 20...
Soar asked 15/12, 2010 at 15:25
4
Solved
I am currently converting a C++ program into CUDA code, and part of my program runs a fast Fourier transform. Originally I ran FFTW, but I saw that I couldn't call it in kernel, so I then rewrote t...
1
Solved
I have a time series data
I am trying to find the fft .But it gives keyerror :Aligned when trying to get the value
my data looks like below
this is the code:
import datetime
import numpy as np
imp...
Orenorenburg asked 1/4, 2022 at 11:43
2
I try to implement the spatial spectrum from the above equation (attached)
Where kX, kY are the grid points in k space,
C(w,r) - cross spectral densities between the i'th and j'th sensor(here it i...
Janik asked 19/1, 2022 at 9:47
1
I am trying to decompose the periodicities present in a signal into its individual components, to calculate their time-periods.
Say the following is my sample signal:
You can reproduce the signal ...
Henryson asked 14/4, 2022 at 19:17
1
Solved
I want to estimate the fourier transform for a given image of size BxCxWxH
In previous torch version the following did the job:
fft_im = torch.rfft(img, signal_ndim=2, onesided=False)
and the outp...
Classified asked 17/3, 2022 at 15:57
4
Solved
I went through how DCT (discrete cosine transform) is used in image and video compression standards.
But why DCT only is preferred over other transforms like dft or dst?
Subtile asked 20/4, 2013 at 10:31
2
Solved
I need to implement a lowpass filter in Python, but the only module I can use is numpy (not scipy). I tried using np.fft.fft() on the signal, then setting all frequencies which are higher than the ...
Alika asked 23/1, 2022 at 18:5
2
Solved
i can get magnitude of signal coming from .wav file , but how to get the phase of that signal too ,,,
Here is the where i browse for .wav file and extract the signal
def browse_wav(self):
file...
Pellegrini asked 25/3, 2017 at 16:48
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