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    1   /*
    2    * Copyright 2003-2004 The Apache Software Foundation.
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  package org.apache.commons.math.stat.descriptive.rank;
    17
    18  import java.io.Serializable;
    19
    20  import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
    21
    22  /***
    23   * Returns the minimum of the available values.
    24   * <p>
    25   * <ul>
    26   * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
    27   * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
    28   * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
    29   * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
    30   * </ul>
    31   * <p>
    32   * <strong>Note that this implementation is not synchronized.</strong> If
    33   * multiple threads access an instance of this class concurrently, and at least
    34   * one of the threads invokes the <code>increment()</code> or
    35   * <code>clear()</code> method, it must be synchronized externally.
    36   *
    37   * @version $Revision: 1.1 $ $Date: 2004/10/08 05:08:17 $
    38   */
    39  public class Min extends AbstractStorelessUnivariateStatistic implements Serializable {
    40
    41      /*** Serializable version identifier */
    42      static final long serialVersionUID = -2941995784909003131L;
    43
    44      /***Number of values that have been added */
    45      private long n;
    46
    47      /***Current value of the statistic */
    48      private double value;
    49
    50      /***
    51       * Create a Min instance
    52       */
    53      public Min() {
    54          n = 0;
    55          value = Double.NaN;
    56      }
    57
    58      /***
    59       * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
    60       */
    61      public void increment(final double d) {
    62          if (d < value || Double.isNaN(value)) {
    63              value = d;
    64          }
    65          n++;
    66      }
    67
    68      /***
    69       * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
    70       */
    71      public void clear() {
    72          value = Double.NaN;
    73          n = 0;
    74      }
    75
    76      /***
    77       * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
    78       */
    79      public double getResult() {
    80          return value;
    81      }
    82
    83      /***
    84       * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
    85       */
    86      public long getN() {
    87          return n;
    88      }
    89
    90      /***
    91       * Returns the minimum of the entries in the specified portion of
    92       * the input array, or <code>Double.NaN</code> if the designated subarray
    93       * is empty.
    94       * <p>
    95       * Throws <code>IllegalArgumentException</code> if the array is null or
    96       * the array index parameters are not valid.
    97       * <p>
    98       * <ul>
    99       * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
    100      * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
    101      * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
    102      * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
    103      * </ul>
    104      *
    105      * @param values the input array
    106      * @param begin index of the first array element to include
    107      * @param length the number of elements to include
    108      * @return the minimum of the values or Double.NaN if length = 0
    109      * @throws IllegalArgumentException if the array is null or the array index
    110      *  parameters are not valid
    111      */
    112     public double evaluate(final double[] values,final int begin, final int length) {
    113         double min = Double.NaN;
    114         if (test(values, begin, length)) {
    115             min = values[begin];
    116             for (int i = begin; i < begin + length; i++) {
    117                 min = (min < values[i]) ? min : values[i];
    118             }
    119         }
    120         return min;
    121     }
    122 }