64 lines
1.7 KiB
C
64 lines
1.7 KiB
C
/*
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* Library: lmfit (Levenberg-Marquardt least squares fitting)
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*
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* File: demo/curve1.c
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*
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* Contents: Example for fitting data with error bars:
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* fit a data set (x,y+-dy) by a curve f(x;p).
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*
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* Author: Joachim Wuttke <j.wuttke@fz-juelich.de> 2004-2013
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*
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* Licence: see ../COPYING (FreeBSD)
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*
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* Homepage: apps.jcns.fz-juelich.de/lmfit
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*/
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#include "lmcurve_tyd.h"
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#include <stdio.h>
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/* model function: a parabola */
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double f( double t, const double *p )
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{
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return p[0] + p[1]*t + p[2]*t*t;
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}
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int main()
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{
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int n = 3; /* number of parameters in model function f */
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double par[3] = { 100, 0, -10 }; /* really bad starting value */
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/* data points: a slightly distorted standard parabola */
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int m = 9;
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int i;
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double t[9] = { -4., -3., -2., -1., 0., 1., 2., 3., 4. };
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double y[9] = { 16.6, 9.9, 4.4, 1.1, 0., 1.1, 4.2, 9.3, 16.4 };
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double dy[9] = { 4, 3, 2, 1, 2, 3, 4, 5, 6 };
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lm_control_struct control = lm_control_double;
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lm_status_struct status;
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control.verbosity = 1;
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printf( "Fitting ...\n" );
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/* now the call to lmfit */
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lmcurve_tyd( n, par, m, t, y, dy, f, &control, &status );
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printf( "Results:\n" );
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printf( "status after %d function evaluations:\n %s\n",
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status.nfev, lm_infmsg[status.outcome] );
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printf("obtained parameters:\n");
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for ( i = 0; i < n; ++i)
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printf(" par[%i] = %12g\n", i, par[i]);
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printf("obtained norm:\n %12g\n", status.fnorm );
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printf("fitting data as follows:\n");
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for ( i = 0; i < m; ++i)
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printf(
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" t[%1d]=%2g y=%5.1f+-%4.1f fit=%8.5f residue=%8.4f weighed=%8.4f\n",
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i, t[i], y[i], dy[i], f(t[i],par), y[i] - f(t[i],par),
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(y[i] - f(t[i],par))/dy[i] );
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return 0;
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}
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