1 /*
2 * Library: lmfit (Levenberg-Marquardt least squares fitting)
3 *
4 * File: demo/curve1.c
5 *
6 * Contents: Example for curve fitting with lmcurve():
7 * fit a data set y(x) by a curve f(x;p).
8 *
9 * Note: Any modification of this example should be copied to
10 * the manual page source lmcurve.pod and to the wiki.
11 *
12 * Author: Joachim Wuttke <j.wuttke@fz-juelich.de> 2004-2013
13 *
14 * Licence: see ../COPYING (FreeBSD)
15 *
16 * Homepage: apps.jcns.fz-juelich.de/lmfit
17 */
18
19 #include "lmcurve.h"
20 #include <stdio.h>
21
22 /* model function: a parabola */
23
f(double t,const double * p)24 double f( double t, const double *p )
25 {
26 return p[0] + p[1]*t + p[2]*t*t;
27 }
28
main()29 int main()
30 {
31 int n = 3; /* number of parameters in model function f */
32 double par[3] = { 100, 0, -10 }; /* really bad starting value */
33
34 /* data points: a slightly distorted standard parabola */
35 int m = 9;
36 int i;
37 double t[9] = { -4., -3., -2., -1., 0., 1., 2., 3., 4. };
38 double y[9] = { 16.6, 9.9, 4.4, 1.1, 0., 1.1, 4.2, 9.3, 16.4 };
39
40 lm_control_struct control = lm_control_double;
41 lm_status_struct status;
42 control.verbosity = 9;
43
44 printf( "Fitting ...\n" );
45 /* now the call to lmfit */
46 lmcurve( n, par, m, t, y, f, &control, &status );
47
48 printf( "Results:\n" );
49 printf( "status after %d function evaluations:\n %s\n",
50 status.nfev, lm_infmsg[status.outcome] );
51
52 printf("obtained parameters:\n");
53 for ( i = 0; i < n; ++i)
54 printf(" par[%i] = %12g\n", i, par[i]);
55 printf("obtained norm:\n %12g\n", status.fnorm );
56
57 printf("fitting data as follows:\n");
58 for ( i = 0; i < m; ++i)
59 printf( " t[%2d]=%4g y=%6g fit=%10g residue=%12g\n",
60 i, t[i], y[i], f(t[i],par), y[i] - f(t[i],par) );
61
62 return 0;
63 }
64