pp_wavelet — Single-level discrete wavelet coefficient transform¶
Group: Augmentation · C ABI: n4m_transform_wavelet_*
Description¶
Single-level DWT coefficient transform.
Parameters¶
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API and bindings¶
C ABI (ABI 2): n4m_transform_wavelet_create · n4m_transform_wavelet_destroy · n4m_transform_wavelet_output_cols · n4m_transform_wavelet_transform. Use the linked public header for the exact signature, configuration, and result handles.
Python (verified public re-export):
from n4m.transform.wavelet import Wavelet
Source signature: Wavelet(family: str = 'haar', mode: str = 'periodization').
R: no current source-verified entry point was found for this catalog method.
MATLAB / Octave: no current source-verified entry point was found for this catalog method.
Explanations¶
Bibliographic source¶
Mallat (1989), A theory for multiresolution signal decomposition: the wavelet representation, IEEE TPAMI 11, 674–693, https://doi.org/10.1109/34.192463.
Mathematical principle¶
A one-level analysis filter bank convolves each spectrum with the selected wavelet’s low-pass and high-pass filters and downsamples by two. Approximation coefficients are concatenated with detail coefficients; the configured extension mode determines edge samples.
Appropriate uses¶
Separating coarse spectral shape from fine-scale detail or supplying wavelet-domain features to a model.
Limits and validation¶
The coefficients are shift-sensitive and their length/order depend on wavelet family, boundary mode, and input width. They are not on the original wavelength grid.
Implementation¶
n4m.transform.wavelet.Wavelet wraps n4m_transform_wavelet_*; orchestration is in preprocessing/wavelets/wavelet.c and shared filters are in wavelet_kernels.c.
The ABI-2 implementation is the n4m_transform_wavelet_* lifecycle in libn4m.
Sources and provenance¶
https://doi.org/10.1109/34.192463; https://github.com/GBeurier/nirs4all-methods/blob/main/cpp/src/core/preprocessing/wavelets/wavelet.c; https://github.com/GBeurier/nirs4all-methods/blob/main/cpp/src/core/common/wavelet_kernels.c
See also: methods index · interactive dashboard