added weighted average - rScore now uses weighted average

rowers/utils.py

@@ -319,3 +319,15 @@ def my_dict_from_instance(instance,model):
             thedict[fname] = (verbosename,value)
 
     return thedict
+
+def wavg(group, avg_name, weight_name):
+    """ http://stackoverflow.com/questions/10951341/pandas-dataframe-aggregate-function-using-multiple-columns
+    In rare instance, we may not have weights, so just return the mean. Customize this if your business case
+    should return otherwise.
+    """
+    d = group[avg_name]
+    w = group[weight_name]
+    try:
+        return (d * w).sum() / w.sum()
+    except ZeroDivisionError:
+        return d.mean()