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 (at) 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 24 double f( double t, const double *p ) 25 { 26 return p[0] + p[1]*t + p[2]*t*t; 27 } 28 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
