Fixed Mutual Information cost function. There was an error when calculating H (Y) with Pr (Y = y) = 0.

Author: gustavoem

src/functions/MutualInformation.cpp

@@ -91,9 +91,9 @@ double MutualInformation::calculate_MI (ElementSubset * X)
     // H(Y) -= Pr(Y=y) * log (Pr(Y = y))
     //
     double Pr_Y_is_y = (double) freq_Y[i] / (double) m;
-
-    H_Y -=  Pr_Y_is_y * (log (Pr_Y_is_y) /
-                        log ((double) set->get_number_of_labels ()));
+    if (Pr_Y_is_y > 0)
+        H_Y -=  Pr_Y_is_y * (log (Pr_Y_is_y) / 
+                log ((double) set->get_number_of_labels ()));
   }
 
   delete [] freq_Y;