GNU R Levenberg-Marquardt nonlinear least-squares algorithm found in MINPACK

 The nls.lm function provides an R interface to lmder and lmdif from the
 MINPACK library, for solving nonlinear least-squares problems by a
 modification of the Levenberg-Marquardt algorithm, with support for
 lower and upper parameter bounds. The implementation can be used via nls-
 like calls using the nlsLM function.