Github user thvasilo commented on a diff in the pull request:
https://github.com/apache/flink/pull/861#discussion_r33356107
--- Diff:
flink-staging/flink-ml/src/main/scala/org/apache/flink/ml/math/ContinuousHistogram.scala
---
@@ -0,0 +1,337 @@
+/*
+ * 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.flink.ml.math
+
+import scala.Double.MaxValue
+import scala.collection.mutable
+
+/** Implementation of a continuous valued online histogram
+ * Adapted from Ben-Haim and Yom-Tov's Streaming Decision Tree Algorithm
+ * Refer http://www.jmlr.org/papers/volume11/ben-haim10a/ben-haim10a.pdf
+ *
+ */
+case class ContinuousHistogram(
+ capacity: Int,
+ min: Double,
+ max: Double)
+ extends OnlineHistogram {
+
+ require(capacity > 0, "Capacity should be a positive integer")
+ require(lower < upper, "Lower must be less than upper")
+
+ val data = new mutable.ArrayBuffer[(Double, Int)]()
+
+ /** Adds a new instance
+ *
+ * @param p value to be added
+ */
+ override def add(p: Double): Unit = {
+ require(p > lower && p < upper, p + " not in (" + lower + "," + upper
+ ")")
+ // search for the index where the value is just higher than p
+ val search = find(p)
+ // add the new value there, shifting everything to the right
+ data.insert(search, (p, 1))
+ // If we're over capacity or any two elements are within 1e-9 of each
other, merge.
+ // This will take care of the case if p was actually equal to some
value in the histogram and
+ // just increment the value there
+ mergeElements()
+ }
+
+ /** Merges the histogram with h and returns a histogram with capacity B
+ *
+ * @param h histogram to be merged
+ * @param B capacity of the resultant histogram
+ * @return Merged histogram with capacity B
+ */
+ override def merge(h: OnlineHistogram, B: Int): ContinuousHistogram = {
+ h match {
+ case temp: ContinuousHistogram => {
+ val m: Int = bins
+ val n: Int = temp.bins
+ var i, j: Int = 0
+ val mergeList = new mutable.ArrayBuffer[(Double, Int)]()
+ while (i < m || j < n) {
+ if (i >= m) {
+ mergeList.+=((temp.getValue(j), temp.getCounter(j)))
+ j = j + 1
+ } else if (j >= n) {
+ mergeList.+=(data.apply(i))
+ i = i + 1
+ } else if (getValue(i) <= temp.getValue(j)) {
--- End diff --
Can't this be combined with the previous case? i.e.
```scala
} else if (j >= n || getValue(i) <= temp.getValue(j)) {
mergeList += data.apply(i)
i = i + 1
```
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
