3 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
22 #include <gsl/gsl_math.h>
23 #include <gsl/gsl_errno.h>
24 #include <gsl/gsl_chebyshev.h>
26 int gsl_cheb_calc_deriv(gsl_cheb_series * deriv, const gsl_cheb_series * f)
28 const size_t n = f->order + 1;
29 const double con = 2.0 / (f->b - f->a);
32 if(deriv->order != f->order)
34 GSL_ERROR ("order of chebyshev series must be equal", GSL_ENOMEM);
37 /* set the other parameters in the chebyshev struct */
43 deriv->err = n * n * f->c[n-1]; /* error in derivative is n^2 c_n */
46 /* FIXME: should probably set deriv->f[] as well */
51 deriv->c[n-2] = 2.0 *(n-1.0) * f->c[n-1];
53 for(i = n-3; i>0; i--)
54 deriv->c[i] = deriv->c[i+2] + 2.0 *(i+1.0) * f->c[i+1];
56 deriv->c[0] = deriv->c[2] + 2.0 * f->c[1];
58 for(i = 0 ; i<n ; i++)