get_best_params         Get best-fit parameters
get_functions           Get nonlinear functions from a separable
                        nonlinear formula
get_lhs                 Get left hand side of a formula
get_parameters          Get parameters from a formula
get_rhs                 Get right hand side of a formula
is.nlstac               Is nlsTAC class check
nls_tac                 Nonlinear fit with the TAC algorithm
predict.nlstac          Predict a nls tac fit.
print.summary.nlstac    Prints the summary a summary.nlstac object.
summary.nlstac          Summary a nls tac fit.
