1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17package org.apache.commons.math.stat.descriptive;
18
19/**
20 * Extends the definition of {@link UnivariateStatistic} with
21 * {@link #increment} and {@link #incrementAll(double[])} methods for adding
22 * values and updating internal state.
23 * <p>
24 * This interface is designed to be used for calculating statistics that can be
25 * computed in one pass through the data without storing the full array of
26 * sample values.</p>
27 *
28 * @version $Revision: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $
29 */
30public interface StorelessUnivariateStatistic extends UnivariateStatistic {
31
32    /**
33     * Updates the internal state of the statistic to reflect the addition of the new value.
34     * @param d  the new value.
35     */
36    void increment(double d);
37
38    /**
39     * Updates the internal state of the statistic to reflect addition of
40     * all values in the values array.  Does not clear the statistic first --
41     * i.e., the values are added <strong>incrementally</strong> to the dataset.
42     *
43     * @param values  array holding the new values to add
44     * @throws IllegalArgumentException if the array is null
45     */
46    void incrementAll(double[] values);
47
48    /**
49     * Updates the internal state of the statistic to reflect addition of
50     * the values in the designated portion of the values array.  Does not
51     * clear the statistic first -- i.e., the values are added
52     * <strong>incrementally</strong> to the dataset.
53     *
54     * @param values  array holding the new values to add
55     * @param start  the array index of the first value to add
56     * @param length  the number of elements to add
57     * @throws IllegalArgumentException if the array is null or the index
58     */
59    void incrementAll(double[] values, int start, int length);
60
61    /**
62     * Returns the current value of the Statistic.
63     * @return value of the statistic, <code>Double.NaN</code> if it
64     * has been cleared or just instantiated.
65     */
66    double getResult();
67
68    /**
69     * Returns the number of values that have been added.
70     * @return the number of values.
71     */
72    long getN();
73
74    /**
75     * Clears the internal state of the Statistic
76     */
77    void clear();
78
79    /**
80     * Returns a copy of the statistic with the same internal state.
81     *
82     * @return a copy of the statistic
83     */
84    StorelessUnivariateStatistic copy();
85
86}
87