Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/3022#discussion_r21655814
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/clustering/GMMExpectationMaximization.scala
---
@@ -0,0 +1,283 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.mllib.clustering
+
+import breeze.linalg.{DenseVector => BreezeVector, DenseMatrix =>
BreezeMatrix}
+import breeze.linalg.{Transpose, det, inv}
+import org.apache.spark.rdd.RDD
+import org.apache.spark.mllib.linalg.{Matrices, Vector, Vectors}
+import org.apache.spark.{Accumulator, AccumulatorParam, SparkContext}
+import org.apache.spark.SparkContext.DoubleAccumulatorParam
+
+/**
+ * Expectation-Maximization for multivariate Gaussian Mixture Models.
+ *
+ */
+object GMMExpectationMaximization {
+ /**
+ * Trains a GMM using the given parameters
+ *
+ * @param data training points stored as RDD[Vector]
+ * @param k the number of Gaussians in the mixture
+ * @param maxIterations the maximum number of iterations to perform
+ * @param delta change in log-likelihood at which convergence is
considered achieved
+ */
+ def train(data: RDD[Vector], k: Int, maxIterations: Int, delta: Double):
GaussianMixtureModel = {
+ new GMMExpectationMaximization().setK(k)
+ .setMaxIterations(maxIterations)
+ .setDelta(delta)
+ .run(data)
+ }
+
+ /**
+ * Trains a GMM using the given parameters
+ *
+ * @param data training points stored as RDD[Vector]
+ * @param k the number of Gaussians in the mixture
+ * @param maxIterations the maximum number of iterations to perform
+ */
+ def train(data: RDD[Vector], k: Int, maxIterations: Int):
GaussianMixtureModel = {
+ new
GMMExpectationMaximization().setK(k).setMaxIterations(maxIterations).run(data)
+ }
+
+ /**
+ * Trains a GMM using the given parameters
+ *
+ * @param data training points stored as RDD[Vector]
+ * @param k the number of Gaussians in the mixture
+ * @param delta change in log-likelihood at which convergence is
considered achieved
+ */
+ def train(data: RDD[Vector], k: Int, delta: Double):
GaussianMixtureModel = {
+ new GMMExpectationMaximization().setK(k).setDelta(delta).run(data)
+ }
+
+ /**
+ * Trains a GMM using the given parameters
+ *
+ * @param data training points stored as RDD[Vector]
+ * @param k the number of Gaussians in the mixture
+ */
+ def train(data: RDD[Vector], k: Int): GaussianMixtureModel = {
+ new GMMExpectationMaximization().setK(k).run(data)
+ }
+}
+
+/**
+ * This class performs multivariate Gaussian expectation maximization. It
will
+ * maximize the log-likelihood for a mixture of k Gaussians, iterating
until
+ * the log-likelihood changes by less than delta, or until it has reached
+ * the max number of iterations.
+ */
+class GMMExpectationMaximization private (
--- End diff --
It might be good to rename this class to "GaussianMixtureModelEM" so that
its name is closer to the name of the model it produces.
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