Changes in version 4.0.0 (2026-09-08)                  

New features

  - Added Raman/SERS spectral preprocessing functions:
    raman_crop_spectra(), raman_despike(), airPLS_fast_dataset(),
    raman_normalize() and raman_sgolay_derivative().

  - Added Raman/SERS peak-analysis functions: raman_find_peaks(),
    raman_align_peaks() and raman_normalize_peak_features().

  - Added optional Fourier and Haar wavelet feature extraction through
    raman_transform_fourier() and raman_transform_wavelet().

  - Added interactive PCA 3D score plots with pca_scoresplot3D() and
    improved support for non-consecutive principal-component selections
    in 3D PCA visualizations.

Improvements

  - Improved input validation, documentation and reproducible examples
    for Raman/SERS and PCA workflows.

  - Improved compatibility of PCA 3D group colouring for metadata
    factors with unused levels.

                 Changes in version 3.1.8 (2026-08-05)                  

  - Fixed malformed roxygen example blocks.
  - Added and improved \value{} documentation in .Rd files.
  - Removed commented example code and improved example robustness for
    checks.
  - Improved documentation consistency.
  - Updated package metadata.

                        Changes in version 3.1.7                        

  - Fixed CRAN resubmission issues related to optional dependencies.
  - Updated repository links and package metadata.
  - Improved package documentation.