pp_weighted_snv — Weighted standard normal variate¶
Group: Signal transforms · C ABI: n4m_transform_weighted_snv_*
Description¶
Weighted standard normal variate normalization.
Parameters¶
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API and bindings¶
C ABI (ABI 2): n4m_transform_weighted_snv_create · n4m_transform_weighted_snv_destroy · n4m_transform_weighted_snv_fit · n4m_transform_weighted_snv_is_fitted · n4m_transform_weighted_snv_transform. Use the linked public header for the exact signature, configuration, and result handles.
Python (verified public re-export):
from n4m.transform.scatter import WeightedSNV
Source signature: WeightedSNV(weights = None, ddof: int = 0, eps: float = 1e-12).
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¶
No single canonical paper defines this exact weighted estimator. It generalizes the SNV transform of Barnes, Dhanoa & Lister (1989), https://doi.org/10.1366/0003702894202201.
Mathematical principle¶
Fit validates and normalizes supplied nonnegative wavelength weights, or uses uniform weights. For every row it computes weighted mean and variance, applies the configured ddof correction, floors variance by eps, and standardizes all wavelengths with that weighted location and scale.
Appropriate uses¶
Reducing scatter while making trusted or diagnostically useful wavelength regions dominate the normalization statistics.
Limits and validation¶
Weights require scientific justification and can bias the whole row statistic toward a small band. Negative/zero-total weights are invalid, and normalization can remove absolute amplitude information.
Implementation¶
n4m.transform.scatter.WeightedSNV uses n4m_transform_weighted_snv_*; normalized weights and weighted moments are in cpp/src/c_api/c_api_advanced.cpp.
The ABI-2 implementation is the n4m_transform_weighted_snv_* lifecycle in libn4m.
Sources and provenance¶
https://doi.org/10.1366/0003702894202201; https://github.com/GBeurier/nirs4all-methods/blob/main/cpp/src/c_api/c_api_advanced.cpp#L526-L635
See also: methods index · interactive dashboard