A Comparison of R Tools for Nonlinear Least Squares Modeling

Our Google Summer of Code project "Improvements to `nls()`" investigated rationalizing R tools for nonlinear regression and nonlinear estimation tools by considering usability, maintainability, and functionality, especially for a Gauss-Newton solver. <!-- JN: copyedit essentially accepted --> The rich features of `nls()` are weakened by several deficiencies and inconsistencies such as a lack of stabilization of the Gauss-Newton solver. Further considerations are the usability and maintainability of the code base that provides the functionality `nls()` claims to offer. Various packages, including our `nlsr`, provide alternative capabilities. We consider the differences in goals, approaches, and features of different tools for nonlinear least squares modeling in R. Discussion of these matters is relevant to improving R generally as well as its nonlinear estimation tools.