# Questions tagged [frequency]

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1 vote
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### How can I use fast Fourier transform to divide into low and high frequency components? [closed]

I have this data (where x is time (seconds) and y is diopters (D)): ...
• 81
71 views

### How to plot time-frequency evolution based on zero crossings?

In a paper that analyzes the data from GW150914, a time-frequency plot was shown. The paper proposes that, quote: An approximate version of the time-frequency evolution can also be obtained directly ...
68 views

### Find FWHM from a plot of real part of complex equation

I am plotting the Real part of a complex equation which looks like this: for now, using the FindMaximum function I can get the max y and max x of the plot, any ideas on how to get the FWHM of this ...
108 views

### amplitude frequency response in mathematica

I am solving the Rayleigh-Plesset equation, which includes the forcing. I want to plot a frequency-amplitude relation numerically in Mathematica, but I am unable to do it. I am providing the Non-...
• 81
333 views

### Time domain to Frequency domain: Simple question

I have an input sine wave of: f=60 Hz. a[x_]= Sin[(2*\[Pi]*f) * x]; If I want to have an input, the same sine wave but in the frequency domain, how it can be ...
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120 views

### Fourier transform on analogue signal to frequency domain

Hi I have a question regarding the Fourier transform of an analogue signal measured in time domain. The current 3 data is normalised, and it is expressed in percentage. I have tried using this line of ...
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538 views

### How can I get the power spectrum density and separate low and high frequencies?

Good day everyone, I'm new in mathematica. I got these values over time (each value was obtained every 100 milliseconds): ...
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1 vote
157 views

### Collect Exponential With Pattern

I have some enormous expression with many complex exponentials. Some of these are time varying, others are just phase terms. Here is a small piece of the expression that I hope fully captures the ...
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419 views

I refurbished my post in order to be more understandable. After computing simulations of Chladni patterns with Mathematica (see my previous topics), I finally went to practice. I realized my own ...
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### What is the syntax for using Reap and Sow and WhenEvent with derivative = 0 with interpolating function?

I have a system of three ODEs. This system oscillates. I need to determine the frequency of each of the three solutions. My file. You can download and modify this. I'm new to Mathematica and I know ...
• 187
116 views

### Input a frequency distribution with unequal class widths and estimate the mean and median

The websites I have visited and the texts available to me determine the mean of an unequal frequency distribution using mean = Sum(class marks x frequency) / Sum(frequency). This is an example I ...
302 views

### How to determine the frequency of oscillations in system of three ODEs?

I want to determine the frequency of oscillations in a system of three stiff ODEs (Oregonator model). That model describes a chemical oscillator. I have a slightly more advanced model of the default ...
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105 views

### FindFit low speed when fitting polynomial coefficients: is it possible to significantly increase the speed?

I work in Mathematica with a Butterworth filter, the transfer function of which depends on the selected order and cutoff frequency. I want to evaluate the change in the location of the roots on the ...
• 2,404
217 views

### Identifying the three frequencies using fourier transform

The following simple function has clearly three frequency components: ...
• 433
527 views

### How can I add two sin waves of different amplitude and frequency? [closed]

I've been tearing up the internet, but I can only find explanations for adding two sine waves of same amplitude and frequency, two sine waves of different amplitudes, or two sine waves of different ...
1 vote
500 views

### Another way to calculate frequency from Fourier transform

I have some trouble with calculating frequency after Fourier transform. My code: ...
• 573
1 vote
306 views

### Fourier transform of non-uniform sampled data

I need to perform an inverse Fourier transform of this set of data, which is in the frequency domain (the x-axis is in $\mu$Hz). However, I'm having two doubts $-$ firstly, this spectral spacing is ...
• 86
837 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 ...
• 43
58 views

### Solving an equation in a specfic region

Good morning, I want to find a solution to the following equation: \left|u\cdot\sin\left(2\pi\cdot f\cdot t\right)\right|=u\cdot\exp\left(-\frac{t}{a}\right)\space\Longleftrightarrow\space t=\dots\...
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1 vote
370 views

### frequency shift in Fourier transform

Have a bit of an analysis issue with Fourier transform of a sinusoidal signal: I have a piece of signal that represents spatial scanning of a pattern. xcoordinate is distance and y is amplitude. I'm ...
• 13
659 views

### Plotting complex number wrt frequency

I want to plot a complex function wrt frequency. How can i do it? If my function as follows: w=2*Pi*f; Zc=(1/i*w*C) Zl=(i*w*L) Z1=(R*Zc)/(1+Zc*Zl) where i==> ...
275 views

### FindFit and Frequency Data

I wrote a code in Mathematica, which tries to match the data by using a weighted sum of 4-parameter beta distribution. I have real-world frequency data, that look like the below image. In the latter, ...
• 35
305 views

### How to find frequency from graph after i solve equation by using NDSolve

How i can find a frequency from graph after i solve equation by using NDsolve. I try to find frequency, and after that i want to plot a graph frequency versus alpha. This is my code ...
1k views

### Frequency decomposition of an mp3 file?

After loading an mp3 file test = Import["test.mp3"] I would like to make a plot with x-axis being the frequency of waveforms ...
• 12k
1 vote
1k views

### Automatically finding frequency

For example we have a sinusoidal function and we want to find frequency of this function/ For those we use Discrete Fourier Transform. Code: ...
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1 vote
1k views

### Re and Im of fourier transform for shifted rectangular pulse

I'm currently trying to vizualize the relation between time and frequency domain and their behavior for a single rectangular pulse regarding different paramters. A special focus is set on the real Re ...
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141 views

### Why does Continuous Wavelet Transform have phase information at high frequencies?

I'm playing around with ContinuousWaveletTransform using a sine wave of a constant frequency: ...
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99 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 ...
• 101
1 vote
874 views

### Image Filtering in the frequency domain

Here is a good starting to fiter image in the frequency domain lena = ColorSeparate[ImageResize[ExampleData[{"TestImage", "Lena"}],{121,121}]][[1]]; (Create a ...
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1 vote