Response Surface Analysis R package RSA version 0.10.8 Advanced response surface analysis. The main function RSA computes and compares several nested polynomial regression models (full second- or third-order polynomial, shifted and rotated squared difference model, rising ridge surfaces, basic squared difference model, asymmetric or level-dependent congruence effect models). The package provides plotting functions for 3d wireframe surfaces, interactive 3d plots, and contour plots. Calculates many surface parameters (a1 to a5, principal axes, stationary point, eigenvalues) and provides standard, robust, or bootstrapped standard errors and confidence intervals for them. Software Depends: R (>= 2.15.0), lavaan (>= 0.5.20), ggplot2, lattice Imports: plyr, RColorBrewer, aplpack, methods Suggests: fields, rgl, qgraph, tcltk, tkrplot, testthat, covr Felix Schönbrodt <felix@nicebread.de> Comprehensive R Archive Network (CRAN) Felix Schönbrodt [cre, aut], Sarah Humberg [aut] GPL (>= 2) 2025-09-26 application/tgz https://CRAN.R-project.org/package=RSA doi:10.32614/CRAN.package.RSA