Changes in version 1.0.0                        

Initial Release

This is the first release of the tptest package, a port of the Stata
tptest command for R.

Features

  - tptest(): Main function for turning point and inflection point tests
    
      - Sasabuchi (1980) / Lind-Mehlum (2010) test for U-shape detection
      - Support for quadratic, cubic, inverse, and log-quadratic forms
      - Delta-method standard errors and confidence intervals
      - Works with lm, glm, and other standard model objects

  - fieller_ci(): Fieller (1954) confidence intervals for turning points
    
      - More robust when denominator coefficient has high uncertainty
      - Handles bounded, unbounded, and degenerate cases

  - twolines_test(): Simonsohn (2018) two-lines test
    
      - Alternative validation for U-shaped relationships
      - Splits data at turning point and tests slope signs

  - Parametric bootstrap confidence intervals

  - S3 methods: print(), summary(), plot(), coef(), confint()

Data

  - ekc: Environmental Kuznets Curve example dataset
      - Simulated panel data for 50 countries over 10 years
      - Demonstrates inverse U-shaped relationship

Documentation

  - Complete roxygen2 documentation with examples
  - References to key papers with DOIs
  - README with usage examples