1 files changed, 45 insertions, 0 deletions
diff --git a/gsl-1.9/doc/examples/fitting.c b/gsl-1.9/doc/examples/fitting.c
new file mode 100644
index 0000000..5c36969
--- /dev/null
+++ b/gsl-1.9/doc/examples/fitting.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <gsl/gsl_fit.h>
+
+int
+main (void)
+{
+  int i, n = 4;
+  double x[4] = { 1970, 1980, 1990, 2000 };
+  double y[4] = {   12,   11,   14,   13 };
+  double w[4] = {  0.1,  0.2,  0.3,  0.4 };
+
+  double c0, c1, cov00, cov01, cov11, chisq;
+
+  gsl_fit_wlinear (x, 1, w, 1, y, 1, n, 
+                   &c0, &c1, &cov00, &cov01, &cov11, 
+                   &chisq);
+
+  printf ("# best fit: Y = %g + %g X\n", c0, c1);
+  printf ("# covariance matrix:\n");
+  printf ("# [ %g, %g\n#   %g, %g]\n", 
+          cov00, cov01, cov01, cov11);
+  printf ("# chisq = %g\n", chisq);
+
+  for (i = 0; i < n; i++)
+    printf ("data: %g %g %g\n", 
+                   x[i], y[i], 1/sqrt(w[i]));
+
+  printf ("\n");
+
+  for (i = -30; i < 130; i++)
+    {
+      double xf = x[0] + (i/100.0) * (x[n-1] - x[0]);
+      double yf, yf_err;
+
+      gsl_fit_linear_est (xf, 
+                          c0, c1, 
+                          cov00, cov01, cov11, 
+                          &yf, &yf_err);
+
+      printf ("fit: %g %g\n", xf, yf);
+      printf ("hi : %g %g\n", xf, yf + yf_err);
+      printf ("lo : %g %g\n", xf, yf - yf_err);
+    }
+  return 0;
+}