Questions tagged [discrete-wavelet-transform]
The discrete-wavelet-transform tag has no usage guidance.
29
questions
0
votes
0
answers
15
views
Discrete wavelet transform - DWT (beginner)
I recently stumbled upon this article: A wavelet-based multivariate multi scale approach for forecasting (PDF)
In the paper they use DWT and I am having trouble understanding how to construct them. ...
2
votes
0
answers
24
views
Estimation of scaling exponent in the wavelet leaders multi-fractal formalism
I am trying to extract multi-fractal features from time-series data
by estimating the singularity spectrum using the wavelet leaders multi-fractal formalism (WLMF) method. Specifically, I want to be ...
0
votes
0
answers
27
views
Adjust Wavelet output to CNN
I want to extract features from the signal using DWT and then feed the results into CNN, after calling the 'dwt' library function I got a runtime error.
...
1
vote
1
answer
38
views
The downsampling step with discrete wavelet transform
For one stage discrete wavelet transform (DWT), if we have a signal with 1000 samples occupying the frequency range from zero to 500 Hz, the output of the low-pass filter is a signal with frequency ...
1
vote
1
answer
34
views
Discrete wavelet decomposition over detail coefficients
per my understanding, if we take a 3-level discrete wavelet decomposition (DWT) over a 1-D signal with sampling rate $F_s$, we will get a series of detail and approximation coefficients, ex: [cA3, cD3,...
0
votes
0
answers
27
views
Difference between Discrete Wavelet Transform and convolution
Sorry in advance if my question is too dumb.
I'm going through the book of Mallat, and from what I understand, the approximation/wavelet coefficients $a_j[n] = <f, \phi_{j,n}>$ and $d_j[n] = <...
1
vote
0
answers
22
views
Function reconstruction after a DWT
I'm new to this field, my apologies if my question sounds too naive.
From what I understood, a function can be decomposed using the scaling function at a given scale $\{\phi_{J, k}\}_{k \in \mathbb{Z}}...
0
votes
0
answers
18
views
Discrete Wavelet Transform: x-axis differences between python and MATLAB
This might be simimlar to the question: Why is there an amplitude difference in Matlab and Python?. But with the difference that I am focusing on the x-axis.
To do a 5th-level decomposition, the used ...
1
vote
0
answers
22
views
1D Interpolating subdivision for wavelet lifting schemes
I am looking into wavelet lifting methods first introduced by Swelden, and explained in this paper: Build your own wavelets at home.
In this paper (in chapter 2 specifically), they discuss ...
1
vote
1
answer
34
views
Polyphase Filter Implementation for oversampled (undecimated) wavelet lifting scheme?
I am learning about lifting schemes, and for my project, it seems as though it would be beneficial to use an undecimated wavelet transform (UWT).
I have found a paper by Lee, Lee, and Yoo (New lifting ...
0
votes
0
answers
23
views
Calculate and plot CDF 5/3 wavelet phi and psi functions
For a FOSS project I've to work with the CDF 5/3 wavelet. And while I understand the implementation by lifting scheme and my code works well, I want to understand the math theory behind wavelets in ...
1
vote
1
answer
56
views
How to do appcoef and detcoef using pyWavelets?
I am new to signal processing and currently doing a school project in wavelet transform using Python. I want to extract all details and approximations (Example: cA2, cA1, cD2, cD1), pywt could return ...
0
votes
0
answers
31
views
Multilevel DWT wavedec - How to get each coefficient (approximations and details) in the same length as the original signal?
I am doing a school project referring to the research paper https://www.tandfonline.com/doi/abs/10.1080/0952813X.2013.813976?journalCode=teta20
The overall concept of the research is as the following ...
1
vote
1
answer
62
views
Should i use window with hop_size in Wavelet Transform or Discrete Wavelet Transform?
I have a signal (audio - voice) with 1 second of duration with sample rate of 50000 Hz. It is big signal and I wish extract some features and apply pattern recognition or classification.
My question ...
2
votes
1
answer
173
views
How could I do a Discrete Fourier Transform in Python if my data is non uniform?
I have been trying to find a way to transform my time series data in an equivalent manner to the discrete Fourier transform. What I wish to find is something like:
...
1
vote
1
answer
97
views
What exactly is meant by "translation invariant dictionaries/wavelets"?
I'm trying to wrap my head around the notion of translation invariance in terms of dictionaries/wavelets. For example in Lecture Notes, Page 41 its written that one starts with a family of atoms/...
0
votes
0
answers
18
views
Inverse discrete wavelet transfrom
I am trying to understand the formula of the inverse wavelet transform. Although I have looked at many papers none of them fully define the summations that appear and this is creating a lot of ...
4
votes
3
answers
521
views
Continuous Wavelet Transform vs Discrete Wavelet Transform
The discrete wavelet transform is applied in many areas, such as signal compression, since it is easy to compute. I notice that, However, the continuous wavelet transform (CWT) is also applied to ...
0
votes
0
answers
44
views
Extract signals with certain frequenceis from a data sample using python
I did not major in signal processing, and I do not know a lot about some possibly very basic facts, so although SE has some questions related to this, I still have some confusion.
I am given a data ...
0
votes
0
answers
37
views
Problem with creating wavelet transform
I am trying to create time-frequency representation of my brain signal. I would like to create the data for frequencies from 0hz - 120hz (so it can cover, delta, theta, alpha, beta, low-gamma and high-...
2
votes
3
answers
108
views
What does the intensity values on wavelet transform mean? Amplitude or power?
So when applying wavelet transform, we get a 2d plot. Each point in that 2d plot has a color, showing intensity of something. But I cannot understand if it is an amplitude or power?
1
vote
0
answers
94
views
How to find the Wavelet measurement matrix in compressed sensing?
Assume that an image vector x = Ψs. s is a sparse vector in which the image vector x of length N x 1 is sparse in the wavelet Ψ basis.
I have issue in finding the measurement matrix A= φ Ψ where φ is ...
1
vote
1
answer
157
views
Waveform pattern detection in time series
I have some IMU data which I am using to detect activity patterns - walking, running etc.
In order to differentiate one activity from another I need to do pattern matching in time series. Different ...
1
vote
0
answers
107
views
Wavelet, scaling, detail, and smooth/approximation coefficients
I was reading through the documentation for the R wavelets package and doing a little experimentation and noticed that the modwt ...
0
votes
0
answers
427
views
PyWavelets SWT versus MODWT
I'm just learning about wavelets and the PyWavelets package. I saw a reference to MODWT, which led me to the SO post here and then to this Python package: https://github.com/pistonly/modwtpy
What ...
1
vote
0
answers
39
views
Pros/Cons to using Spectral and Diffusive Graph Wavelets
As I understand, there are two major methods of constructing wavelets on graphs. Spectral wavelets, from David K Hammond et. al, and diffusive wavelets from Coifman and Maggioni. I can't quite parse ...
2
votes
0
answers
32
views
What does the sample entropy of a digital signal mean?
What sample entropy signifies about a signal and how it used to analyse a signal?
1
vote
1
answer
75
views
Why discrete wavelet transforms use sampling rate 2 and need signal length to be a power of 2?
I know Fourier transforms but new to wavelet transforms. I can understand Haar transform needs signal length a power of 2, since the filters have 2 taps and down-sampling and up-sampling in the ...
1
vote
1
answer
40
views
Does the Fast Wavelet Transform produce the same coefficient as the Discrete Wavelet Transform?
Does the Fast Wavelet Transform(FWT) produce the same coefficients as the Discrete Wavelet Transform(DWT) if configured for the same depths? Or is the the FWT just an approximation of the DWT?