1 files changed, 72 insertions, 0 deletions
diff --git a/gsl-1.9/doc/examples/ntupler.c b/gsl-1.9/doc/examples/ntupler.c
new file mode 100644
index 0000000..a926522
--- /dev/null
+++ b/gsl-1.9/doc/examples/ntupler.c
@@ -0,0 +1,72 @@
+#include <math.h>
+#include <gsl/gsl_ntuple.h>
+#include <gsl/gsl_histogram.h>
+
+struct data
+{
+  double x;
+  double y;
+  double z;
+};
+
+int sel_func (void *ntuple_data, void *params);
+double val_func (void *ntuple_data, void *params);
+
+int
+main (void)
+{
+  struct data ntuple_row;
+
+  gsl_ntuple *ntuple 
+    = gsl_ntuple_open ("test.dat", &ntuple_row,
+                       sizeof (ntuple_row));
+  double lower = 1.5;
+
+  gsl_ntuple_select_fn S;
+  gsl_ntuple_value_fn V;
+
+  gsl_histogram *h = gsl_histogram_alloc (100);
+  gsl_histogram_set_ranges_uniform(h, 0.0, 10.0);
+
+  S.function = &sel_func;
+  S.params = &lower;
+
+  V.function = &val_func;
+  V.params = 0;
+
+  gsl_ntuple_project (h, ntuple, &V, &S);
+  gsl_histogram_fprintf (stdout, h, "%f", "%f");
+  gsl_histogram_free (h);
+  gsl_ntuple_close (ntuple);
+
+  return 0;
+}
+
+int
+sel_func (void *ntuple_data, void *params)
+{
+  struct data * data = (struct data *) ntuple_data;  
+  double x, y, z, E2, scale;
+  scale = *(double *) params;
+  
+  x = data->x;
+  y = data->y;
+  z = data->z;
+
+  E2 = x * x + y * y + z * z;
+
+  return E2 > scale;
+}
+
+double
+val_func (void *ntuple_data, void *params)
+{
+  struct data * data = (struct data *) ntuple_data;  
+  double x, y, z;
+
+  x = data->x;
+  y = data->y;
+  z = data->z;
+
+  return x * x + y * y + z * z;
+}