A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero.
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17 views
Implementing 1-D Wavelet transform in MATLAB
I am trying to implement 1-D CWT on a Tiva-C board. To understand the CWT I wrote a simple MATLAB code without using inbuilt functions. I am getting some results but they do not match with the results ...
2
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2answers
63 views
Other time-frequency-plane tiling than STFT, DWT, ConstantQ-Transform: multiresolution STFT?
It is known that
a) the STFT gives a rectangular tiling of the time-frequency plane
b) the Wavelet transform gives a non-linear tiling (better frequency resolution for low-frequencies, and better ...
-1
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1answer
28 views
RMS value from wavelet coefficients
I am confused on how to calculate the RMS value fo a signal from the wavelet coefficients. Here is a minimal python code for a sinusoidal sigmal of amplitude $1$ and $RMS=1/\sqrt{2}$
...
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0answers
21 views
Understanding wavelets via 1-D PyWavelet example
I have been reading about wavelets for few weeks now and I have bumped into subjects like scaling functions, wavelet functions, filter banks and multiresolution analysis. Despite reading and getting ...
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1answer
32 views
Find Fourier series $f(t) = e^{jx t}$ , $−\pi < t < \pi$ [closed]
I need to find the Fourier series of the $f(t) = e^{jxt}$ , $− \pi < t < \pi$
What will be the first step to solve it?
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0answers
32 views
Efficient audio power spectrum estimation
I am working on a small personal project where I want to control a matrix of roughly 100 actuators with an audio stream. The goal would be that the user can see/feel the music features in the movement ...
1
vote
1answer
66 views
wavelet decomposition for time series signal
Is it possible to use stationary wavelet decomposition as a tool to extract wavelet features for a time series? I can see how it works for image cases, but for a time series prediction problem say $...
1
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1answer
28 views
Reproducing paper results about a wavelet transformation using python [closed]
I have been reading this PhD theis about wavelets and I am trying to reproduce some of the results but I don't know the specific code to use to generate similar results.
The original time series ...
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0answers
21 views
Understanding this continuous haar wavelet implementation
This is the implementation I am referring to, found here:
...
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1answer
37 views
Phase of a signal with multi delayed windowed (rectangular window) signal with different amplitudes
I have a signal $x(t)$ which is composed of multi delayed linear chirps with different amplitudes and phases but they share the same $w$ and $\alpha$, the signal can be expressed as follows:
$$\...
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1answer
31 views
Dimensional reduction from DWT with threshold
I have been trying to find out how can the discrete wavelet transform (DWT) be possible to reduce dimension of data.
Then I saw the question which is seemingly related to my work:
Feature extraction/...
1
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3answers
108 views
Denoising a signal
I'm starting hydraulic experiments, where I'd have to measure velocity in an unsteady flow with a device called Acoustic Doppler Velocimeter. In DSP terms, I'd have a nonstationary signal in a shape ...
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0answers
25 views
From Fourier (k space) to wavelet domain in MRI sensing
In compressed sensing MRI (cSENSE MRI) technology the idea seems to entail sampling from the Fourier domain (k space) in a way that, when transformed to the wavelet domain ("sparsification"), the ...
2
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2answers
74 views
Orthonormal Dictionaries for Band Limited Signals
If $\mathbf{x} = [x_0, x_1, \ldots, x_{N-1}]^T$ is the time sampled input signal and $\mathbf{Y} = [Y_0, Y_1, \ldots, Y_{N-1}]^T$ is the Fourier transform of the input signal, then a linear ...
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1answer
42 views
Detection of Troughs and Notches in a PPG Signal
I'm working a project which tries to determine Blood Pressure from PPG signals.I'm trying to extract the features as shown below...
I'm having problem in finding the troughs and dicrotic notch for ...
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0answers
31 views
signal denoising by continuous wavelet transform
i want to use Morlet mother wavelet for signal denoising so i should employ cwt only. Is there any proper MATLAB code for this target?
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0answers
169 views
How does the Scipy implementation of CWT actually work?
I'm trying to use the SciPy implementation of the Continuous Wavelet Transform to analyze EEG data.
I am using The problem is that I have no idea what the width parameter should be. It says that it's ...
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0answers
95 views
How to interpret Discrete Wavelet Transform Coefficients?
I want to extract features from DWT coefficients like Power Spectral Density, Max frequency, Min frequency etc.
After taking DWT, we get coefficients D1, D2, A2 etc. But my question is, Are D1, D2, ...
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0answers
77 views
Wavelet transform and FFT using to extract feature power bands with EEG signals
I am using 5 channels [ fz , cz , c3 , c4 , pz] to detect drowsiness of driver
My First Question is, what is the right input to get feature power band ( Theta , alpha , gamma , beta ) to wavelet ...
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0answers
12 views
Do the magnitude of the signal changes in the wavelet filtering
I am using Daubechies 4 wavelets to extract a required signal.
In my signal there is a magnitude change. My raw signal lies from $-3$ to $3$, but when I choose the detail coefficients of the Db4 ...
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1answer
33 views
Isolating frequency-specific oscillation from transient
I am performing time-frequency analysis on electrophysiological data with complex morlet wavelets. Each decomposition in the attached figure shows total power following the onset of a stimulus (top ...
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0answers
36 views
Determine scales for continuous wavelet transform (cwt) obtained
How to obtain the corresponding scales for frequencies while computing cwt in Matlab or any other formulae?
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0answers
24 views
Does a “chirp”-like generalization of the Gabor or Morlet wavelets definitions exist in the lit somewhere?
I have asked this at the Math SE also.
Predicating this on the definition of the continuous Fourier Transform preferred by most electrical engineers:
$$ X(f) \triangleq \mathscr{F} \Big\{ x(t) \Big\}...
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0answers
14 views
Wavelet central frequency
What is the definition of the central frequency of a Wavelet and the bandwidth of a Wavelet? How do they affect the resultant waveform of the wavelet?
Thanks.
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0answers
37 views
Algorithm Question for Haar Scaling Function and Discrete wavelet transform
Let $\displaystyle f(x)= \begin{cases} 4x^2-4x+1 & 0\le x\le 1, \\ 0 & \text{otherwise}. \end{cases} $
a) Find the approximation $f_{-3}$ of $f \in V_{-3}$ using the Haar scaling function
...
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197 views
Plot CWT (Continuous Wavelet Transform) in 3D using Python
I am working on a project using signal processing.
Part of my work is to apply the CWT on the signal I have.
As I read, that I can plot the signal in the frequency-time domain using CWT.
So my ...
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0answers
13 views
Implementing Wavelet family matrices
I want to use CS to reconstruct an image from fewer samples, and I would like to use wavelet coefficients but I don't know how to define them when making a Psi matrix.
I have written wavelets ...
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0answers
8 views
Wavelet Quality factor
I read in my lectures that a wavelet should have a constant quality factor Q but without any explanation. Can anyone please explain what do we mean by a quality factor. Thanks..
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1answer
40 views
Can I apply CWT on a digital signal?
First, I am so sorry for my dumb and stupid question, I am very beginner with signals.
Say that I have an ultrasonic sensor cabled to an ADC (Analog to Digital Converter).
The ADC converts the analog ...
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0answers
25 views
Daubechies orthogonal Wavelets
I read a document that it said: "Daubechies orthogonal wavelets D2-D5". Then I've searched on the Internet to get information about this kind but I haven't found any information about it. Moreover, to ...
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0answers
20 views
Qrs complex detection using haar wavelet
I am using this algorithm to detect QRS complex from ECG signal that is samled at 360Hz that is decomposed to level 5 with haar wavelet
In the fourth step it says that the duration of the QRS ...
1
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0answers
17 views
why is my inbuilt function is not matching with the db5 CA and CD coefficients generated by my code
I am working on wavelet decomposition.As read by the theory i have implemented wavelet decomposition in MATLAB. CA and CD for wavelet decomposition of db1 matches with the inbuilt function but not ...
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1answer
40 views
Alternative function for Matlab Stationary Wavelet Transformation
I'm currently working on a project of mine where I have to use stationary wavelet transformation. I found a perfect way to do the transformation using wavelet toolbox of the Matlab. But since it is ...
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0answers
63 views
How to define the scales in a biorthogonal, dyadic Discrete Wavelet Transform in Python
I am sorry if this has been discussed before but I could not find any answer.
I am trying to implement an algorithm that I found in a paper which asks for a biorthogonal, dyadic DWT with scales 1 and ...
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0answers
47 views
wavelet reconstruction
I am doing mtech project now.
Actually I am working on discrete wavelet transform.I have done till wavelet decomposition. I have been stuck in reconstructing the signal back to original .please help ...
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2answers
184 views
How to implement a filter associated to a specific wavelet
I am working on ECG signals, to eventually extract features in order to detect an arrhythmia and classify it.
I am using Discrete Wavelet Transform with biorthogonal wavelet bior6.8
During my research,...
2
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2answers
186 views
How to extract features of individual spikes in non-negative signal?
I have data of non-negative (in the sense there's no signal below baseline) spiking waveforms, which are in the form of a 1D array of numbers:
Spikes that cross some threshold are considered real ...
2
votes
3answers
102 views
Denoise techniques when clean signal and pure noise is available
I have the clean version of the signal.
I can obtain the environmental noise.
I want to apply an effective denoising technique on a noisy signal (i.e., clean plus environmental noise).
Some ...
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1answer
74 views
What the entropy equations mean?
In wavelet packet image compression, different types of entropy methods can be used, like Shannon and log-energy.
Shannon entropy uses this equation $\mathrm{ent}= -\sum (x^2 \times \log(x^2))$, ...
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0answers
103 views
Log energy and Shannon entropy?
For best tree decomposition using wavelet packets, i have tried both Shannon and log energy entropy functions. I noticed that log energy leads to images with higher PSNR values. Could you please help ...
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0answers
677 views
Applying a wavelet transform to a 1D time series
I'm preprocessing a non-stationary financial time series as input for a machine learning algorithm, and I'm trying to reduce noise in my data. All the research I've looked at points towards wavelet ...
3
votes
0answers
57 views
Selection of transforms, windows, wavelets for current signal analysis
I am new to this topic but I already read about the propperties of different signal analysis methods. I am stuck with the obvious advantages of FFT, STFT and Wavelet transforms but can't find good ...
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0answers
313 views
Calculating and plotting Wavelet Power Spectral Density
I would like to calculate the power spectrum of the wavelet coefficients for an observed signal and compare it with the Fourier power spectrum of the same signal. I want to do this to show how the ...
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0answers
9 views
Obtaining a fixed number of wavelet coefficients from variable-length inputs
I recently discovered wavelet transforms, and have studied some work done using them to create (meta-)features for machine learning classifiers. However, all the work I've seen thus far uses images/...
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0answers
47 views
Daubechies Transform Example on Integer Array
I'm very new to wavelet transforms and I've had difficulty in finding examples that do a good job illustrating the steps clearly enough for me to turn those steps into code. One of the best sources I'...
2
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0answers
1k views
Discrete wavelet transform: visualizing relation between decomposed detail coefficients and signal
I'm trying to directly visualize the relation between discrete wavelet transform (DWT) detail coefficients and the original signal/its reconstruction. The goal is to show their relation in an ...
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0answers
36 views
I want to understand the Dual Tree Complex Wavelet Transform
I want to understand the dual tree complex wavelet transform for vibration analysis of motor faults.I search a lot of books and materials but couldn't understand
Can anyone recommend me a book or ...
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1answer
66 views
Wavelets and bank filters
The wavelet transform has a problem as it gives poor time resolution for low frequencies and poor frequency resolution for high frequencies according to uncertainty conditions.
This appears well ...
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0answers
61 views
Frequency Response of MODWT Filters at Various Scales
I am trying to find the frequency response for wavelet filters -- specifically MODWT wavelet filters at various scales (for scales 1, 2,3, 4,..).
Given a MODWT filter at Scale 1 (Daubechies 4-tap):
...
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1answer
46 views
Question about normalization before estimate the spectrum
I work with a Electrophysiologist Team and i have seen something who interrogate me (i'm a noobs in DSP).
They acquires a signal into a brain structure (an LFP to be precise) :
in a first time they ...
