1 files changed, 63 insertions, 0 deletions
diff --git a/gsl-1.9/cheb/deriv.c b/gsl-1.9/cheb/deriv.c
new file mode 100644
index 0000000..57c22df
--- /dev/null
+++ b/gsl-1.9/cheb/deriv.c
@@ -0,0 +1,63 @@
+/* cheb/deriv.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_chebyshev.h>
+
+int gsl_cheb_calc_deriv(gsl_cheb_series * deriv, const gsl_cheb_series * f)
+{
+  const size_t n = f->order + 1;
+  const double con = 2.0 / (f->b - f->a);
+  size_t i;
+  
+  if(deriv->order != f->order) 
+    {
+      GSL_ERROR ("order of chebyshev series must be equal", GSL_ENOMEM);
+    }
+  
+  /* set the other parameters in the chebyshev struct */
+
+  deriv->a = f->a;
+  deriv->b = f->b;
+
+#ifdef ERR
+  deriv->err = n * n * f->c[n-1];   /* error in derivative is n^2 c_n */ 
+#endif
+
+  /* FIXME:  should probably set deriv->f[] as well */
+  
+  deriv->c[n-1] = 0.0;
+  
+  if(n > 1) {
+    deriv->c[n-2] = 2.0 *(n-1.0) * f->c[n-1];
+
+    for(i = n-3; i>0; i--) 
+      deriv->c[i] = deriv->c[i+2] + 2.0 *(i+1.0) * f->c[i+1];
+
+    deriv->c[0] = deriv->c[2] + 2.0 * f->c[1];
+
+    for(i = 0  ; i<n ; i++) 
+      deriv->c[i] *= con;
+  }
+
+  return GSL_SUCCESS;
+}