nirs4all.utils.header_units module

Centralized header unit utilities for consistent handling across the codebase.

This module provides a single source of truth for: - Axis labels based on header unit type - X-values extraction from headers - Axis orientation (for wavenumber inversion)

All visualization code should use these utilities instead of inline logic.

nirs4all.utils.header_units.parse_numeric_headers(headers: list[str] | None) → ndarray | None

Parse headers into a float array, tolerating a trailing unit suffix (e.g. "852.78_nm").

Accepts plain numbers and numbers with a known unit suffix (nm/µm/cm-1), with an optional _/-/space separator. Returns None if any header is not such a value, so the caller can fall back to indices or raise — rather than silently mining a number out of arbitrary text like "feature_852.78_nm".

nirs4all.utils.header_units.should_invert_x_axis(x_values: ndarray) → bool

Check if x-axis should be inverted (for wavenumber convention).

In spectroscopy, wavenumber (cm⁻¹) axes are often displayed in descending order (high to low) if the data is ordered that way.

Parameters:

x_values – Array of x-axis values

Returns:

True if x_values are in descending order and should be displayed as such