Simplex Regression Models with Parametric or Fixed Mean Link Functions // Fits and analyzes simplex regression models with either fixed or parametric mean link functions. Implements the simplex probability density function, cumulative distribution function, quantile function, random number generation, and variance evaluation. Offers several fixed and parametric link functions for the mean submodel, tools for residual analysis and diagnostic plotting, hypothesis testing procedures, and influence measures such as Cook's distance and leverage (hat values). Includes the Scout Score (SS) criterion for model selection, enabling comprehensive inference and diagnostic analysis within the simplex regression framework. For more details see Barndorff-Nielsen and Jorgensen (1991) doi:10.1016/0047-259X(91)90008-P and Justino and Cribari-Neto (2026) doi:10.1016/j.apm.2025.116713.