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Questions tagged [continuous-fourier]

Use this tag for questions about computation of exact continuous-time Fourier transform (e.g. using symbolic software like Sage, Mathematica, Sympy). For the discrete Fourier transform and fast Fourier transform, use tag [fft].

63 questions
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Represent data as Fourier-transformation or polynomial with high degree?

I am dealing with stelar light curves (.fits-files containing 4000 datapoints of time vs stelar brigthness, see graphic for a few examples with different periodicity). I need to represent/fit these lightcurves in a way that allows me to perform on…
NeStack
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Plotting Fourier Series coefficients in Python using Simpson's Rule

I want to 1. express Simpson's Rule as a general function for integration in python and 2. use it to compute and plot the Fourier Series coefficients of the function . I've stolen and adapted this code for Simpson's Rule, which seems to work fine…
Aran G
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How to find the symbolic Fourier transform expression?

I was doing some basic problems in Fourier transform and using MATLAB to verify my answers. I encountered a problem when I tried to find the Fourier transform expression of the following two signals: y1 = 2*exp(-t)u[t] + 5*exp(-(t-1)/2)u[t-1] y3 =…
Zero_Cool
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A Fourier Series Matlab code

I have created this code in order to calculate and sketch the Fourier Coefficients A0 ,An ,and Bn without using Fourier Series command but,unfortunately the plots results did not look like a Fourier Series. if someone please guide me to solve this…
jack lee
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Computing and plotting the spectrum of a signal using FFT on Matlab

I am missing something in the computation of the spectrum of my signal using FFT on Matlab. My code: %% compute the spectrum of the data (data(t)) L = length(time); % length of the sample NFFT = 2^(nextpow2(L)-1); % Next power of 2 from length of…
LeChat
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Using Fourier transform to calculating the average of the power spectrum

I want to know is there any way to write a code for this expression? I don't know how I can define t' in this expression. on the other hand the integration varies from -inf to +inf.
D.matlab
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How to calculate efficiently and accurately the Fourier transform of a radial function in Fortran

As my question states, I want to calculate the Fourier transform F(q) of a radial function f(r) (defined on [0,infinity[ and which decays like an exponential exp(-Ar +b) at large r) as accurately as possible in Fortran. The function values come from…
mwoua
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Approximation by sin waves using DFT on python. What's wrong?

I'm writing the prorgram on python that can approximate time series by sin waves. The program uses DFT to find sin waves, after that it chooses sin waves with biggest amplitudes. Here's my code: __author__ = 'FATVVS' import math # Wave -…
faceless wanderer
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Optimizing Fourier Series Fitting Function Matlab

I am trying to iterate through a set of samples that seems to show periodic changes. I need continuously apply the fit function to get the fourier series coefficients, the regression has to be n samples in the past (in my case, around 30). The…
Luis Cruz
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Why does the frequency spectra change when the sampling frequency is changed?

Here is my code for generating a triangular waveform in the time domain and for generating its corresponding fourier series/transform (I don't know whether its series or transform because matlab only has fourier transform function but since the…
Mahrrkiee
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Fast Fourier Transform and Time-Series Forecasting in R

After reviewing the literature available for FFT, I saw very little documentation of employing FFT for macroeconomic data. Can you please give sources to utilize FFT using time-series data in R? Thank you for your time.
Economic Hedge
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Simulating of Fraunhofer Diffraction of Zigzags by 2D FFT

I tried to study the diffraction pattern of the following zigzag grating by Matlab(FFT of this image).. And the result showed like this(please ignore the scale bar in this img) I think the program of FFT by Matlab is correct.. I am just wondering…
Cici
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why do we need all pass filter in frequency domain

Here is mostly what we do, firstly we transform signal from time domain to frequency domain, then we will operate on the frequency domain with different filters, such as band filter, low pass filter, all pass filter. What I don't understand is that…
hellocoding
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Does Fourier Transform only process periodic signal?

The aperiodic signal could be processed by DFT. DFT can process both periodic and aperiodic signal?
hellocoding
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Finding Percent Error of a Fourier Series

Find the error as a function of n, where the error is defined as the difference between two the voltage from the Fourier series (vF (t)) and the value from the ideal function (v(t)), normalized to the maximum magnitude (Vm ): I am given this prompt…
Mystery Man
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