aug_multiplicative_noise — Per-spectrum multiplicative gain noise¶
Group: Augmentation · C ABI: n4m_augmentation_multiplicative_noise_*
Description¶
Apply per-element multiplicative Gaussian noise.
Parameters¶
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API and bindings¶
C ABI (ABI 2): n4m_augmentation_multiplicative_noise_apply · n4m_augmentation_multiplicative_noise_create · n4m_augmentation_multiplicative_noise_destroy. Use the linked public header for the exact signature, configuration, and result handles.
Python (verified public re-export):
from n4m.augmentation.noise import MultiplicativeNoise
Source signature: MultiplicativeNoise(sigma_gain: float = 0.01, rng: Optional[PCG64] = None, seed: int = 0).
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 publication uniquely defines this implementation. It belongs to the family of spectral offset/slope/gain augmentation discussed by Bjerrum et al. (2017), arXiv:1710.01927 (https://arxiv.org/abs/1710.01927).
Mathematical principle¶
One draw is made per row: \(g_i=1+\sigma_g Z_i\), \(Z_i\sim\mathcal N(0,1)\), then \(X'_{ij}=g_iX_{ij}\) for every wavelength. sigma_gain controls relative gain variation, so all channels in a spectrum move together.
Appropriate uses¶
Simulating sample-wise optical gain, concentration scale, or path-length changes.
Limits and validation¶
The public operator implements per-sample gain only: it does not draw an independent gain at every wavelength and does not constrain \(g_i\) to be positive. Large sigma_gain can invert a spectrum.
Implementation¶
Python role API n4m.augmentation.noise.MultiplicativeNoise; ABI 2 family n4m_augmentation_multiplicative_noise_{create,apply,destroy}.
The ABI-2 implementation is the n4m_augmentation_multiplicative_noise_* lifecycle in libn4m.
Sources and provenance¶
https://github.com/GBeurier/nirs4all-methods/blob/main/cpp/src/core/augmentation/noise/multiplicative_noise.h; https://arxiv.org/abs/1710.01927
See also: methods index · interactive dashboard