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Questions tagged [time-frequency]

Time-frequency methods provide more viable solutions than Fourier methods for signals that are shorter in time and not necessarily periodic. Methods such as Wavelet and Gabor transforms are considered to be T-F techniques.

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Applying Fourier Transform on Time Series data and avoiding aliasing

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 the link to data that I've used. After reading the…
Furqan Hashim
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Changing time frequency in Pandas Dataframe

I have a Pandas DataFrame as below. df A B date_time 2014-07-01 06:03:59.614000 62.1250 NaN 2014-07-01 06:03:59.692000 62.2500 NaN 2014-07-01 06:13:34.524000 …
Zhubarb
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Note Synthesis, Harmonics (Violin, Piano, Guitar, Bass), Frequencies, MIDI

I want to find, how notes were built. Example for a Instrument (Violin or Piano), The Note LA4 (A4) has main (or central) frequency FC at 440Hz with a Specific Amplitude AC, but also it must has other frequencies (harmonics?) FH with other…
user1410223
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Testing for periodicity of noisy biological data: periodogram significance?

I'm trying to analyze some noisy time-series data in R. The data are based on the CO2 emission of animals and they show a sort of cyclic periodicity that I'd like to characterize. I'd like to test the hypotheses: H0: There is no cyclic CO2…
James Waters
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How to calculate frequency (freq) when using seasonal decomposition()

I am trying to separate seasonality, trend and residual from timeseries 'XYZ.csv' (sales data collected over 2 years of time). [XYZ.csv contains 2 columns - date and sales. Date has been set as an index within the code.] import pandas as pd import…
Analyst17
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playing low frequency heartbeat signal through mobile speaker

I am making an app to listen to heartbeat . I could listen to filtered heartbeat signal through headset but not through mobile speaker as the mobile speaker doesn't support such low frequencies , I tried frequency shifting , but it results in a…
pavan
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MATLAB Wigner plot for Matching Pursuit atoms

Using MATLAB I apply Matching Pursuit to approximate a signal. My problem is that I struggle to visualize the time-frequency representation of the selected atoms. I'm trying to produce a Wigner plot similar to the following image (source). I have…
imant
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Filter design and frequency extraction in Python

I'm working on a project to find the instantaneous frequency of a multicomponent audio signal in Python. I am currently using a Butterworth bandpass filter combined with scipy.signal.lfilter to extract around my desired frequency region. I then use…
allhands
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EEG Wavelet Analysis

I want to do a time-frequency analysis of an EEG signal. I found the GSL wavelet function for computing wavelet coefficients. How can I extract actual frequency bands (e.g. 8 - 12 Hz) from that coefficients? The GSL manual says: For the forward…
Michael
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Gabor Filter problem

How to design a Gabor Filter for pattern recognition. I just cannot figure it.
Sm1
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image Texture Feature using Gabor filter

I have the following gabor filter to extract image texture feature.. a=imread('image0001.jpg'); a=double(a); a=a-mean(a(:)); [r,c,l]=size(a); K=5; S=6; Uh=0.4; Ul=0.05; alpha=(Uh/Ul)^(1/(S-1)); …
zenab
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Continuous Wavelet Transform with Scipy.signal (Python): what is parameter “widths” in cwt() function? (time-frequency)

I search to draw a time-frequency signal with a discrete temporal signal (sampling step = 0.001sec). I use Python and the library Scipy.signal. I use the function cwt(data, wavelet, widths), which returns a matrix, to do a continuous wavelet…
ArnoNoo
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Pandas: Find end frequency spectrum above a defined threshold

long time reader, first time posting. I am working with x,y data for frequency response plots in Pandas DataFrames. Here is an example of the data and the plots (see full .csv file at end of post): fbc['x'],fbc['y'] (0 [89.25, 89.543, 89.719,…
Brady Volpe
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How to find the fundamental frequency of a wav file

I'm analysing a lot of short .wav files and for a part of the analysis I want to plot the fundamental frequency only of the file. My signal processing is a bit rusty, but I'm now getting plots that look like they should be correct. I'm just not…
Deniz Dohmen
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How to downsample Fourier complex values?

Disclaimer: I'm not a signal processing expert. I'm writing a function that takes a 1D array and performs Fast Fourier Transform on it. Here's how it works: If the array's size is not a power of two, pad it with 0s at the end so that its size…
MathuSum Mut
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