1 files changed, 52 insertions, 0 deletions
diff --git a/gsl-1.9/doc/examples/rootnewt.c b/gsl-1.9/doc/examples/rootnewt.c
new file mode 100644
index 0000000..fea5f11
--- /dev/null
+++ b/gsl-1.9/doc/examples/rootnewt.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_math.h>
+#include <gsl/gsl_roots.h>
+
+#include "demo_fn.h"
+#include "demo_fn.c"
+
+int
+main (void)
+{
+  int status;
+  int iter = 0, max_iter = 100;
+  const gsl_root_fdfsolver_type *T;
+  gsl_root_fdfsolver *s;
+  double x0, x = 5.0, r_expected = sqrt (5.0);
+  gsl_function_fdf FDF;
+  struct quadratic_params params = {1.0, 0.0, -5.0};
+
+  FDF.f = &quadratic;
+  FDF.df = &quadratic_deriv;
+  FDF.fdf = &quadratic_fdf;
+  FDF.params = &params;
+
+  T = gsl_root_fdfsolver_newton;
+  s = gsl_root_fdfsolver_alloc (T);
+  gsl_root_fdfsolver_set (s, &FDF, x);
+
+  printf ("using %s method\n", 
+          gsl_root_fdfsolver_name (s));
+
+  printf ("%-5s %10s %10s %10s\n",
+          "iter", "root", "err", "err(est)");
+  do
+    {
+      iter++;
+      status = gsl_root_fdfsolver_iterate (s);
+      x0 = x;
+      x = gsl_root_fdfsolver_root (s);
+      status = gsl_root_test_delta (x, x0, 0, 1e-3);
+
+      if (status == GSL_SUCCESS)
+        printf ("Converged:\n");
+
+      printf ("%5d %10.7f %+10.7f %10.7f\n",
+              iter, x, x - r_expected, x - x0);
+    }
+  while (status == GSL_CONTINUE && iter < max_iter);
+
+  gsl_root_fdfsolver_free (s);
+  return status;
+}