1 files changed, 67 insertions, 0 deletions
diff --git a/src/statistics.c b/src/statistics.c
new file mode 100644
index 00000000..adadf907
--- /dev/null
+++ b/src/statistics.c
@@ -0,0 +1,67 @@
+/*
+ * statistics.c
+ *
+ * Structure-factor statistics
+ *
+ * (c) 2007-2009 Thomas White <thomas.white@desy.de>
+ *
+ * integr_sim - Test relrod integration
+ *
+ */
+
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <math.h>
+#include <stdlib.h>
+
+
+/* By what (best-fitted) factor must the list "list" be multiplied by,
+ * if it were to be merged with "target"? */
+double stat_scale_intensity(double *obs, double *calc, unsigned int *c,
+                            int size)
+{
+	double top = 0.0;
+	double bot = 0.0;
+	int i;
+
+	for ( i=0; i<size; i++ ) {
+
+		if ( c[i] > 0 ) {
+			double obsi;
+			obsi = obs[i] / (double)c[i];
+			top += obsi * calc[i];
+			bot += calc[i] * calc[i];
+		} /* else reflection not measured so don't worry about it */
+
+	}
+
+	return top/bot;
+}
+
+
+double stat_r2(double *obs, double *calc, unsigned int *c, int size,
+               double *scalep)
+{
+	double top = 0.0;
+	double bot = 0.0;
+	double scale;
+	int i;
+	scale = stat_scale_intensity(obs, calc, c, size);
+	*scalep = scale;
+
+	for ( i=0; i<size; i++ ) {
+
+		if ( c[i] > 0 ) {
+			double obsi;
+			obsi = obs[i] / (double)c[i];
+			top += fabs(obsi/scale - calc[i]);
+			bot += obsi/scale;
+		}
+
+	} /* else reflection not measured so don't worry about it */
+
+	return top/bot;
+}