mgenlq

SciMath

Optimization

mgenlq Nonlinear least squares

Description:

mgenlq finds a parameter vector x^* of size n that minimizes the sum of squares function f(x):

f(x) = 1/2 where: r_i (x) is a twice continuously differentiable function of x

mgenlq requires a user function to compute r_i (x).

Synopsis:

#include<sci.h>

int mgenlq ( int num, int n, double * x, int (*rfun) ( ), int maxf, double est )

Input:

num: Number of components in r(x) (i.e number of observations), num ³ 1

n: Number of elements of vector x (number of parameters)

x: Array of size n, as the initial parameter vector x^*

rfun: User function representing r(x) (Declared external):

int (*rfun)( int *num, int * n, double * x, int * in, double * fx )

Input:

num: Number of components in r(x) (i.e number of observations) (a pointer)

n: Number of elements of vector x (number of parameters) (a pointer )

x: Array of size n, as the initial parameter vector x^*

in: Number of times this function has been called (a pointer)

output

in: Set to zero only if x is out of bounds, otherwise do not change in

fx: Value of r(x) for this vector x

maxf: Maximum number of function evaluations allowed

est: Minimization criteria. Minimization criteria will be met only when:

|| f(x) - f(x^*) || £ est £ ||f(x)|| or when:

|| x-x^* || £ est ( || x || + || x^* || ), where x^* is the solution (Objective vector for minimization) and || x || denotes the Euclidean norm of vector x ( See introduction )

Output:

x: Array of size n, the solution vector x^*

Errors:

In case of a non fatal error, external integer sci_err_code is set to the corresponding error code. Non fatal errors are denoted by a N following the error code. (See Error Handling)

Error Code	Error Description
ERRS1	n < 1
ERRS2	maxf < 1
ERRS3	est £ 0.0
ERRS4 N	Singular convergence ( too many free parameters in x )
ERRS5 N	False convergence ( est may be to small )
ERRS6 N	Number of calls to user function exceeds maxf
ERRS7 N	f(x) could not be evaluated at the initial x vector

Category: Optimization/Minimization/Maximization

See Also: menmin, mensbm, mgennm, mgengm, mgengh

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