Returns the nonlinear functions of a formula as charater strings.
get_functions(form, lp)An array containing the strings for the nonlinear functions of the formula.
Either a string in the form 'y ~ ...' or an object of formula class
A string array with the names of the linear parameters contained in the formula as obtained with get_parameters function
Mariano Rodríguez-Arias (arias@unex.es). Deptartment of Mathematics
Juan Antonio Fernández Torvisco (jfernandck@alumnos.unex.es). Department of Mathematics
University of Extremadura (Spain)
Rafael Benítez (rafael.suarez@uv.es). Department of Business Mathematics
University of Valencia (Spain)
This is an internal function used by nls_tac. A separable nonlinear formula is of the form
$$y ~ a_1 f_1(x;p) + a_2 f_2(x;p) + \ldots + a_n f_n(x;p),$$
where \(f_1\),..., \(f_n\) are general nonlinear functions, \(a_1\),...,\(a_n\), are the linear coefficients and \(p\) is the vector of nonlinear parameters.
The formula given in the input should be of this form and get_functions will return an array with the string expressions of functions \(f_i\).