Add Multinomial Distribution and Modify Examples

src/main/java/blang/distributions/Multinomial.bl

@@ -0,0 +1,42 @@
+package blang.distributions
+
+import static bayonet.distributions.Multinomial.sampleMultinomial
+
+/** A generalization of a Binomial Distribution. Value \in \mathbb{R}^n\). */
+model Multinomial {
+	/** Number of successes for each of the \(n\) categories. */
+	random List<IntVar> numberofSuccesses
+
+	/** Vector of probabilities \((p_0, p_1, \dots, p_{n-1})\) for each of the \(n\) categories. */
+	param Simplex probabilities
+
+	 /** The number of independent trials. Value in \(k > 0\) */
+	param IntVar numberofTrials
+
+	laws{
+
+		logf(numberofTrials) { return logFactorial(numberofTrials) }
+
+		logf(numberofSuccesses, probabilities, numberofTrials) {
+			var sum0 = 0.0
+			for (int i: 0..< numberofSuccesses.size()) {
+				if (probabilities.get(i) < 0.0 || probabilities.get(i) > 1.0) return NEGATIVE_INFINITY
+				if (numberofSuccesses.get(i) < 0.0) return NEGATIVE_INFINITY
+				if (numberofTrials <= 0 || numberofSuccesses.get(i) < numberofTrials) return NEGATIVE_INFINITY
+				sum0 += (numberofSuccesses.get(i) * log(probabilities.get(i)))
+			return sum0
+			}
+		}
+
+		logf(numberofSuccesses, probabilities, numberofTrials) {
+			var sum1 = 0.0
+			for (int i: 0..< numberofSuccesses.size()) {
+				if (numberofSuccesses.get(i) < 0) return NEGATIVE_INFINITY
+				if (numberofTrials <= 0 || numberofSuccesses.get(i) < numberofTrials) return NEGATIVE_INFINITY
+				sum1 += logFactorial(numberofSuccesses.get(i))
+				return sum1
+			}
+		}
+	}
+	generate(rand) {sampleMultinomial(rand, probabilities.vectorToArray)}
+}

src/test/java/blang/Examples.xtend

@@ -87,7 +87,16 @@ class Examples {
   	.build,
   	intRealizationSquared
   )
-
+
+  public val multinomial = add(
+  	new Multinomial.Builder()
+  	  .setProbabilities(fixedSimplex(0.2,0.3,0.5))
+  	  .setNumberofTrials(fixedInt(3))
+  	  .setNumberofSuccesses(latentIntList(3))
+  	    .build,
+  	listHash
+  )
+
   public val hyperGeometric = add(
   	new HyperGeometric.Builder()
   	.setNumberOfDraws(fixedInt(3))