tptest 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