samoa-api/src/main/java/org/apache/samoa/moa/classifiers/core/splitcriteria/SDRSplitCriterion.java

/*
 * 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
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package org.apache.samoa.moa.classifiers.core.splitcriteria;

public class SDRSplitCriterion extends VarianceReductionSplitCriterion {
  private static final long serialVersionUID = 1L;

  public static double computeSD(double[] dist) {
    int N = (int) dist[0];
    double sum = dist[1];
    double sumSq = dist[2];
    return Math.sqrt((sumSq - ((sum * sum) / N)) / N);
  }

}