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Questions tagged [ifft]

NOTE: please use the FFT tag instead. The FFT is a type of algorithm for quickly computing the Inverse Discrete Fourier Transform.

The IFFT is an FFT algorithm with some different initial permutation of data samples, and often an additional normalization, such that the algorithm computes the IDFT rather than the DFT. The FFT and IFFT are always implemented by the same code.

Related topics include , , , .

More information on the IFFT can be found in the Wikipedia article on the FFT

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Hamming Filter in Frequency and Spatial Domain

I want to remove the Gibbs artifact in a 1D signal by applying the Hamming filter on that in MATLAB. What I have is the k1 which is the signal in frequency domain. I can get the signal in time domain by applying DFT on k1: s1 =…
SaraG
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Changing the inverse fast Fourier transform (ifft) to use an arbitrary waveform instead of sine waves to create a new signal

I know that an inverse fast Fourier transform (ifft) sums multiple sine waves together from data obtain from doing an fft on a signal. Is there a way to create a signal using a new type of inverse fast Fourier transform (ifft) using an arbitrary…
Rick T
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WebGL inverse FFT implementation

I am trying to implement an FFT and associated inverse FFT in WebGL using fragment shaders. I am using shader code from this github site. I believe that I am doing the FFT correctly as I am getting results that seem correct however my…
DLH
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FFTshift causes oscillations - why? (numpy)

my original problem was the following: I have a pulse-envelope in an array a (0-element = time 0, last element = time T). I want to fourier spectrum of the pulse. So what I did was np.fft.fftshift(np.fft.fft(a)). All good. But then I was told to…
refle
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Computational Physics, FFT analysis

I solved the following questions for a computational assignment, I got a really bad grade on it (67%) I would like to understand how to properly do these questions, in particular Q1.b and Q3. Please be as detailed as possible, I would really like to…
ಠ_ಠ
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Getting y-axis shift during FFT noise removal

I'm trying to do a noise removal by FFT in R. The trouble I'm having is that I get a y-axis shift during the process and I'm not sure what the cause is. I have read up on FFT and used this resource as a guide. See below for the code I have been…
scs217
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Inverse FFT in Theano

I know that theano.tensor.fourier.fft is essentially numpy.fft.fft. However, I was wondering if the inverse FFT was implemented? Namely, is there something like a theano.tensor.fourier.ifft, which is equivalent to numpy.fft.ifft? I noticed that this…
user19346
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Problems using FFT on multiplication of large numbers

I am recently trying to multiply a bunch (up to 10^5) of very small numbers (order of 10^-4) with each other, so I would end in the order of 10^-(4*10^5) which does not fit into any variable. My approach is the following: Multiply each number by…
el_paco
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TypeError: src data type = 15 is not supported

I want to use Fast Fourier Transform but already trying a simple back and forth transformation doesn't work. The code is import cv2 import numpy as np img = cv2.imread('Picture.bmp',0) f = np.fft.fft2(img) fshift = np.fft.fftshift(f) f_ishift =…
katosh
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How to Inverse FFT in Arduino

I am trying to filter some data based on the the following code using Arduino FFT library for FFT (fast Fourier transform) /* fft_adc_serial.pde guest openmusiclabs.com 7.7.14 example sketch for testing the fft library. it takes in data on ADC0…
user2637015
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FFT Algorithm C Code Explaination

http://www.tech.dmu.ac.uk/~eg/tensiometer/fft/fft.c http://www.tech.dmu.ac.uk/~eg/tensiometer/fft/fft_test.c I have found a good working C Code for FFT Algorithm for converting Time Domain to Frequency Domain and vice versa in the above links. But I…
Psbk
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Strange behaviour when doing a fftw3 MPI Fourier transform from complex to real

Consider a problem where you want to transform a spectral representation of f(x,y) ~ cos(x) to coordinate space. So exp(i*x) + exp(-i*x) ----> f(x,y), where f(x,y) = some_factor * cos(x) . In column-major layout (my example is written below in…
Mali Remorker
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OpenCV DFT_INVERSE different from Matlab's ifft

I try to filter a signal using opencv's dft function. The way I try to this is taking the signal in time domain: x = [0.0201920000000000 -0.0514940000000000 0.0222140000000000 0.0142460000000000 -0.00313500000000000 0.00270600000000000…
CRS
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Computational complexity of Inverse FFT

I am trying to calculate the computational complexity of ifft, I know it’s NlogN for a N*1 dimension, signal. But I have a product of two signals then I want to get ifft, and then calculate the computational complexity. So simply, if X(w) and Q(w)…
SAH
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Matlab - How to fix : Warning: Displaying real part of complex input ?

Given the code function [nImg,mask] = myFunc(img,rl,rh) [n m] = size(img); mask = ones(n, m); % do some stuff % more % and more % fourierImg = fft2(img); % take the fourier transform 2d for the given image …
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