Changes in version 0.3.0 (2025-04-30)                  

Major Improvements

  - Added automatic bandwidth selection using cross-validation or
    Silverman's rule of thumb
  - Improved performance of get_est_Ar() function by approximately 50%,
    significantly accelerating main function execution time
  - Improved code structure with centralized configuration management
  - Added unit tests

New Features

  - Implemented automatic bandwidth selection with two methods:
      - Cross-validation (h_method = "cv") for optimal accuracy
      - Silverman's rule of thumb (h_method = "silverman") for faster
        computation
  - Added create_biasBound_config() function for centralized
    configuration management
  - Added create_kernel_functions() factory for flexible kernel function
    creation
  - Changed default bandwidth parameter h to NULL to enable automatic
    selection

Performance Optimization

  - Optimized get_est_Ar() function by:
      - Precomputing avg_phi_log values for all frequencies
      - Enhancing the optimization algorithm for determining smoothness
        parameters
  - Increased default resolution for kernel function approximation

Bug Fixes and Edge Case Handling

  - Modified get_sigma() and get_sigma_yx() to handle negative density
    estimates by returning 0 instead of NaN
  - Enhanced get_conditional_var() to ensure non-negative variance
    estimates
  - Fixed sinc() function to properly handle x = 0 cases
  - Improved handling of NA values in Fourier transform calculations

Documentation

  - Updated examples to demonstrate automatic bandwidth selection
  - Improved parameter descriptions throughout the package