add comment to groupSizeDistribution Attribute added to AttributeSource

VadereState/src/org/vadere/state/attributes/scenario/AttributesSource.java

@@ -48,7 +48,21 @@ public class AttributesSource extends AttributesEmbedShape {
 	private boolean useFreeSpaceOnly = true;
 	private List<Integer> targetIds = new LinkedList<>();
 
-	private List<Double> groupSizeDistribution = Arrays.asList(0.0, 0.0, 1.0);
+	/**
+	 *  This Attribute only takes affect if a model org.vadere.simulator.models.groups.GroupModel
+	 *  is present in the scenario. When this is the case this list defines the group size
+	 *  distribution of this source. The list can be arbitrary long but must add up to 1.
+	 *  The index of the list represents the size of the  groups and the value the probability
+	 *  index 0 => GroupSize = 1
+	 *  index 1 => GroupSize = 2
+	 *  ...
+	 *
+	 *  Example: ----------------------------------------------------------------------------------
+	 *  probability [ 0.0, 0.0, 0.25, 0.25, 0.25, .... ] ------------------------------------------
+  	 *  GroupSize   [  1    2    3     4     5         ] ------------------------------------------
+	 *  uniform distribution of groups of the size from 3 to 5 ------------------------------------
+	 */
+	private List<Double> groupSizeDistribution = Arrays.asList(1.0);
 
 	/**
 	 * The type of dynamic elements this source creates.