Add some useful methods to explicit.Distribution.

prism/src/explicit/Distribution.java

@@ -29,6 +29,7 @@ package explicit;
 import java.util.BitSet;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
@@ -202,19 +203,65 @@ public class Distribution implements Iterable<Entry<Integer, Double>>
 	}
 
 	/**
-	 * Get the sum of the probabilities in the distribution.
+	 * Get the mean of the distribution.
 	 */
-	public double sum()
+	public double mean()
 	{
 		double d = 0.0;
 		Iterator<Entry<Integer, Double>> i = iterator();
 		while (i.hasNext()) {
 			Map.Entry<Integer, Double> e = i.next();
-			d += e.getValue();
+			d += e.getValue() * e.getKey();
 		}
 		return d;
 	}
 	
+	/**
+	 * Get the variance of the distribution.
+	 */
+	public double variance()
+	{
+		double mean = mean();
+		double meanSq = 0.0;
+		Iterator<Entry<Integer, Double>> i = iterator();
+		while (i.hasNext()) {
+			Map.Entry<Integer, Double> e = i.next();
+			meanSq += e.getValue() * e.getKey() * e.getKey();
+		}
+		return Math.abs(meanSq - mean * mean);
+	}
+	
+	/**
+	 * Get the standard deviation of the distribution.
+	 */
+	public double standardDeviation()
+	{
+		return Math.sqrt(variance());
+	}
+	
+	/**
+	 * Get the relative standard deviation of the distribution,
+	 * i.e., as a percentage of the mean.
+	 */
+	public double standardDeviationRelative()
+	{
+		return 100.0 * standardDeviation() / mean();
+	}
+	
+	/**
+	 * Get the sum of the probabilities in the distribution.
+	 */
+	public double sum()
+	{
+		double mean = 0.0;
+		Iterator<Entry<Integer, Double>> i = iterator();
+		while (i.hasNext()) {
+			Map.Entry<Integer, Double> e = i.next();
+			mean += e.getValue();
+		}
+		return mean;
+	}
+
 	/**
 	 * Get the sum of all the probabilities in the distribution except for index j.
 	 */
@@ -275,4 +322,22 @@ public class Distribution implements Iterable<Entry<Integer, Double>>
 	{
 		return map.toString();
 	}
+	
+	public String toStringCSV()
+	{
+		String s = "Value";
+		Iterator<Entry<Integer, Double>> i = iterator();
+		while (i.hasNext()) {
+			Map.Entry<Integer, Double> e = i.next();
+			s += ", " + e.getKey();
+		}
+		s += "\nProbability";
+		i = iterator();
+		while (i.hasNext()) {
+			Map.Entry<Integer, Double> e = i.next();
+			s += ", " + e.getValue();
+		}
+		s += "\n";
+		return s;
+	}
 }