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From: tillrohrmann <git@git.apache.org>
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Subject: [GitHub] flink pull request: [FLINK-2030][FLINK-2274][ml]Online
 Histograms ...
Content-Type: text/plain
Message-Id: <20150820144214.13800E7DCE@git1-us-west.apache.org>
Date: Thu, 20 Aug 2015 14:42:14 +0000 (UTC)

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/861#discussion_r37536712
  
    --- Diff: flink-staging/flink-ml/src/main/scala/org/apache/flink/ml/statistics/DiscreteHistogram.scala ---
    @@ -0,0 +1,126 @@
    +/*
    + * 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.statistics
    +
    +import scala.collection.mutable
    +
    +/** Implementation of a discrete valued online histogram
    +  *
    +  * =Parameters=
    +  * -[[numCategories]]:
    +  * Number of categories in the histogram
    +  */
    +class DiscreteHistogram(numCategories: Int) extends OnlineHistogram {
    +
    +  require(numCategories > 0, "Capacity must be greater than zero")
    +  val data = new mutable.HashMap[Double, Int]()
    +
    +  /** Number of categories in the histogram
    +    *
    +    * @return number of categories
    +    */
    +  override def bins: Int = {
    +    numCategories
    +  }
    +
    +  /** Increment count of category c
    +    *
    +    * @param c category whose count needs to be incremented
    +    */
    +  override def add(c: Double): Unit = {
    +    data.get(c) match {
    +      case None =>
    +        require(data.size < numCategories, "Insufficient capacity. Failed to add.")
    +        data.put(c, 1)
    +      case Some(value) =>
    +        data.update(c, value + 1)
    +    }
    +  }
    +
    +  /** Merges the histogram with h and returns a new histogram
    --- End diff --
    
    what is *h*? Would be easier to understand if you write *Merges this histogram with the given histogram h. The result is a new histogram* .


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