Fourier ARDL Methods: Quantile, Nonlinear, Multi-Threshold & Unit Root Tests R package fqardl version 1.0.2 Comprehensive implementation of advanced ARDL methodologies for cointegration analysis with structural breaks and asymmetric effects. Includes: (1) Fourier Quantile ARDL (FQARDL) - quantile regression with Fourier approximation for analyzing relationships across the conditional distribution; (2) Fourier Nonlinear ARDL (FNARDL) - asymmetric cointegration with partial sum decomposition following Shin, Yu & Greenwood-Nimmo (2014) <doi:10.1007/978-1-4899-8008-3_9>; (3) Multi-Threshold NARDL (MTNARDL) - multiple regime asymmetry analysis; (4) Fourier Unit Root Tests - ADF and KPSS tests with Fourier terms following Enders & Lee (2012) <doi:10.1016/j.econlet.2012.05.019> and Becker, Enders & Lee (2006) <doi:10.1111/j.1467-9892.2006.00490.x>. Features automatic lag and frequency selection, PSS bounds testing following Pesaran, Shin & Smith (2001) <doi:10.1002/jae.616>, bootstrap cointegration tests, Wald tests for asymmetry, dynamic multiplier computation, and publication-ready visualizations. Ported from Stata/Python by Dr. Merwan Roudane. Software Depends: R (>= 3.5.0) Imports: quantreg (>= 5.0), ggplot2 (>= 3.0.0), tidyr, gridExtra, stats Suggests: testthat (>= 3.0.0), knitr, rmarkdown, plotly, covr Muhammad Alkhalaf <muhammedalkhalaf@gmail.com> Comprehensive R Archive Network (CRAN) Muhammad Alkhalaf [aut, cre, cph] (ORCID: <https://orcid.org/0009-0002-2677-9246>), Merwan Roudane [ctb] (Original Stata/Python implementation) GPL-3 2026-03-17 application/tgz https://CRAN.R-project.org/package=fqardl doi:10.32614/CRAN.package.fqardl