Linked Questions

0
votes
1answer
72 views

How can I make an FFT in Mathematica using data from a file? [closed]

I need to calculate the seismic moment of an earthquake data, but I don't know how the FFT is applied in some data, my data is a plain text that I must import it to Mathematica ...
2
votes
0answers
100 views

Why does Mathematica Fourier transform of finite sequence of numbers require parameters? [closed]

I apologize if this is a basic question, but here goes: The Discrete Fourier transform of a sequence of N complex numbers is uniquely defined by eq.1 in this wiki page, https://en.wikipedia.org/wiki/...
1
vote
1answer
79 views

Fast method for numerical integral (Fouriertransform?)

I want to numerically compute following integral (as fast as possible): \begin{equation} f(x) = \left| \int e^{ \mathrm{i} p x / 2} f(p) \ \mathrm{d}p\right|^2 , \end{equation} where $f(p)$ is given ...
0
votes
1answer
118 views

Using Fourier to get the numerical FT of a Gaussian [duplicate]

I've been trying to find the FT of a more complicated function, but it seems my method is wrong. To check, I tried to calculate the FT of a Gaussian numerically. This is what I did: ...
1
vote
0answers
38 views

Taking Fourier transform with WolframAlpha gives unexpected result [duplicate]

I have noticed that WolframAlpha's definition of the Fourier Transform is different than the one in my book of formulas. In my book the Fourier transform of $f(t)$ is defined as: $$\int_{-\infty}^{\...
1
vote
1answer
107 views

Finding frequency of oscillation of an particle by Fourier analysis of the trajectory [duplicate]

I am trying to find the resonant frequency of a particle by Fourier analysis of the trajectory. Here is the data file. ...
0
votes
0answers
52 views

Finding Fourier transform of a quantity v/s theta (0 to 360 degrees)

I have a physical quantity (experimentally measured) lets say T whose variation I have measured with angle (theta in degrees). I want to find out the Fourier components of this quantity with respect ...
0
votes
1answer
122 views

Identifying the three frequencies using fourier transform

The following simple function has clearly three frequency components: ...
3
votes
1answer
56 views

How does the Fourier transform take its input?

I'm using the Fourier command and I'm wondering how does it take its imput. I know that it takes a list of numbers representing a function of time and it gives back a list of numbers representing a ...
1
vote
0answers
113 views

Taking numerical Laplace transform of a tabulated data with Mathematica?

I am relatively new to the use of Mathematica in the context of numerical evaluations, therefore I would greatly appreciate a detailed answer and would like to express my gratitude towards any help in ...
0
votes
1answer
286 views

Discrete fourier transform and convolution — scaling factor?

I am trying to convolve a square wave (a diffraction grating phgrating with slits size \[CapitalLambda]) with a point spread ...
2
votes
2answers
198 views

Figuring out the frequency components using FFT [duplicate]

The function defined below has three frequencies 2, 4 and 10. How to use the Fourier transform (FFT) to show these frequencies? ...
0
votes
1answer
103 views

How to fit one function into the form of another?

I have a slightly complicated periodic function of one variable t, say g[t]. I want to do a least squares fit of that function ...
0
votes
1answer
194 views

Finding frequency from Fourier transform [closed]

I tried to find frequency using Fourier Transform, but notice that my code have some mistakes which I can't find. So, my code is below: ...
0
votes
1answer
228 views

Periodogram local maximum

I want to find dominant frequencies of periodogram exactly. ...
1
vote
1answer
461 views

Get frequency axis in Fourier transform (and save them)

I am trying to get the Fourier transform of a light-curve (with an even number of points, 300, and equally spaced in time, 6.9 seconds) and my problem is to get the frequency on the x-axis. I can ...
2
votes
1answer
188 views

Discrete Fourier transformation from ASCII (for noob)

I am not familiar with Mathematica (I am a physicist programming in Fortran) and my knowledge of it is very limited, unfortunately. I would like to perform the Fourier trasform of a lightcurve which ...
9
votes
2answers
562 views

Frequency of ticks in mechanical watches

I'm looking to find the frequency of a relatively large dataset (or a relatively short audio file) of a repeating sound, like so: Here are the original files, for those willing to play. :) eta2412 ...
0
votes
0answers
65 views

Frequencies for Fourier coefficients [duplicate]

I have been given the task of calculating the frequencies to which the fourier coefficients correspond. So my input is a discrete signal [1,4,0,1], which gives me <...
23
votes
3answers
5k views

How to make Fourier behave like FourierTransform?

I'm not very experienced with Fourier Transforms, so there may be something inherently wrong with attempting to do this, but how can I make the discrete Fourier behave like the continuous ...
2
votes
1answer
698 views

How to find the Fourier Transform of a list?

I have a list (list) in the form of {x,y} as ...
1
vote
3answers
418 views

DFT: Fourier Plot Not Giving Expected Result

I'm trying use Mathematica to compute the Discrete Fourier Transform (DFT) of a table of data points and then plot the result. As a test run, I took values from the function $x=f(t)=\sin(2\pi t) $ for ...
0
votes
1answer
354 views

Ideal/Brick wall Low/High-pass filters: Fourier approach not working

I am trying to take a signal (as a list) and separate it into the low frequency and high frequency parts around some split frequency f. Given that what little signal processing I ever studied is now ...
0
votes
1answer
1k views

FFT of data to obtain resonance frequencies and correct amplitudes

I have often to do with experimental data (with a certain length and given sampling frequency) where I obtain trajetories of moving objects in 2d. Then I am interested to find out what the ...
21
votes
4answers
6k views

How to calculate the Fourier Transform of a Gaussian pulse with a nonlinear chirp: Cos[ t + Exp[t^2] ]?

I have an optical pulse in time domain: Exp[-t^2] Cos[50 t - Exp[-2 t^2] 8 π]. The figure of this formula is I hope to calculate the Fourier Transform of this ...
2
votes
1answer
110 views

Using ''Module' and 'Table' to Plot 'Fourier'

I'm trying to make a function that outputs a plot given a particular parameter, whilst using the Mathematica functions Module, Fourier, and Table. This is what I've come up with thus far. ...
4
votes
1answer
264 views

Comparing ordinates between FourierTransform and Fourier

I have a test function ff[t_] := Exp[-t^2 - t]. I have calculated the Fourier transform with FourierTransform: ...
2
votes
0answers
81 views

Determining Periodicity with Fourier?

Note: This question has previously been marked as a duplicate of What do the X and Y axis stand for in the Fourier transform domain?. While the answer will likely have an overlap, so the question ...
0
votes
0answers
117 views

Help with Frequency Identification with Fourier? [duplicate]

Note: This question has been marked as a duplicate of What do the X and Y axis stand for in the Fourier transform domain?. While the answer will likely have an overlap, so the question should be ...
0
votes
1answer
203 views

Frequencies doubled in fourier transform [duplicate]

With this code I get a nice plot of the Fourier transform, but the frequencies are doubled. By this I mean that when using a sine wave I generated at 220 Hz, the plot gives me a single peak at 440 Hz. ...
0
votes
0answers
89 views

Identify frequency components

I try to perform data analysis on wind power production. Data consist in 17520 points, corresponding to the production averaged over 30 minutes over the 365 days of the year. I somehow expect to see ...
3
votes
1answer
4k views

Using mathematica to take fourier transform of data

I'm trying to use Mathematica to take a discrete Fourier transform of 68 data points (0 to 67) to perform further analysis. My data points, when plotted, look like this: Pretty straightforward. Now,...
1
vote
2answers
389 views

Parseval identity in one side Fourier Transform

Is there any posibility to apply Parseval identity(energy in time domain is equal to freq. domain) on One/Single-side Fourier transform? In other word for "standard" FT the test Mathematica can be <...
10
votes
1answer
748 views

finding Frequency of Sinewave data using Fourier

CONTEXT I read 5 different related posts but I do not understand how to interpret mathematica's output for my situation. ...
3
votes
1answer
394 views

Fourier Transform accelerogram seismic

I have a seismic accelerogram. I tried to apply the Fourier Transform to interpolate function, but dosn't work. So, i applied the ...
4
votes
1answer
2k views

Why Fourier transform is symmetric no matter what interval I choose? [duplicate]

I'm solving a vibration problem. After solving two systems of ODEs (one valid in 0-0.1 and the other in 0.1-1) I get the plot of 3 functions, one of them is this, the plot of the variable $y_w$ (Image ...
0
votes
1answer
6k views

Discrete Fourier Transform: help on how to convert x axis in to the frequency when I have a set of data samples [duplicate]

I have a huge data set (400000 sample) and when I plot them ListLinePlot[Au4, PlotRange -> {All, All}] I used the following code to Fourier transform it <...
3
votes
2answers
363 views

Discrete Fourier Transform - Inadequate precision and wrong peak positions

I have a small problem with a piece of code. I searched the site but was not able to find an answer to my specific question. I am trying a quick test of the Fourier capabilities (on lists) of ...
5
votes
1answer
3k views

Differences between FFT and analytical Fourier Transform

In MATLAB, if I perform an FFT on a simple Gaussian spot with a phase grating: ...
0
votes
2answers
387 views

Wrong frequency in Fourier

I have a file, filled with data like this: As you can see the approximate frequency is about $5/1000 = 0.005$, then angular frequency is about $2 \pi \times 0.005 \approx 0.03$. Then I use discrete ...
1
vote
2answers
231 views

DataRange in plotting Fourier

I'm trying to estimate a frequency spectrum of a given discrete function. I have a file which is filled of values of Sine-function $sin(t)$, where $t$ runs from $0.0$ to $100.0$ and a discrete step is ...
22
votes
6answers
25k views

How do you find the frequency and amplitude from Fourier?

Edit This is a popular question with several answers. This edit organises the answers and gives links. Fourier just gives y values (ordinates) if you wish to read off frequencies and amplitudes you ...
1
vote
0answers
216 views

Perform a Fourier Transform on a wavelength scan

I have a plot of the power transmitted through a device as a function of wavelength, from 1500 to 1600nm. There is some Fabry-Perot noise, plus I suspect some other regularities. I would like to ...
1
vote
1answer
519 views

DFT: why are frequencies mirrored around the frequency axis?

I want to apply Mathematica's DFT procedure, Fourier[], to a Gaussian. Why a Gaussian? Because I know the analytical result. So I define ...