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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;
17  
18  /**
19   * Extends the definition of {@link UnivariateStatistic} with 
20   * {@link #increment} and {@link #incrementAll(double[])} methods for adding
21   * values and updating internal state.  
22   * <p>
23   * This interface is designed to be used for calculating statistics that can be computed in 
24   * one pass through the data without storing the full array of sample values.
25   *
26   * @version $Revision: 155427 $ $Date: 2005-02-26 06:11:52 -0700 (Sat, 26 Feb 2005) $
27   */
28  public interface StorelessUnivariateStatistic extends UnivariateStatistic {
29  
30      /**
31       * Updates the internal state of the statistic to reflect the addition of the new value.
32       * @param d  the new value.
33       */
34      void increment(double d);
35      
36      /**
37       * Updates the internal state of the statistic to reflect addition of
38       * all values in the values array.  Does not clear the statistic first --
39       * i.e., the values are added <strong>incrementally</stong> to the dataset.
40       * 
41       * @param values  array holding the new values to add
42       * @throws IllegalArgumentException if the array is null
43       */
44      void incrementAll(double[] values);
45      
46      /**
47       * Updates the internal state of the statistic to reflect addition of
48       * the values in the designated portion of the values array.  Does not
49       * clear the statistic first -- i.e., the values are added 
50       * <strong>incrementally</stong> to the dataset.
51       * 
52       * @param values  array holding the new values to add
53       * @param start  the array index of the first value to add
54       * @param length  the number of elements to add
55       * @throws IllegalArgumentException if the array is null or the index
56       */
57      void incrementAll(double[] values, int start, int length);
58  
59      /**
60       * Returns the current value of the Statistic.
61       * @return value of the statistic, <code>Double.NaN</code> if it
62       * has been cleared or just instantiated.
63       */
64      double getResult();
65  
66      /**
67       * Returns the number of values that have been added.
68       * @return the number of values.
69       */
70      long getN();
71  
72      /**
73       * Clears the internal state of the Statistic
74       */
75      void clear();
76  
77  }