001: /*
002: * Copyright 2003-2004 The Apache Software Foundation.
003: *
004: * Licensed under the Apache License, Version 2.0 (the "License");
005: * you may not use this file except in compliance with the License.
006: * You may obtain a copy of the License at
007: *
008: * http://www.apache.org/licenses/LICENSE-2.0
009: *
010: * Unless required by applicable law or agreed to in writing, software
011: * distributed under the License is distributed on an "AS IS" BASIS,
012: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013: * See the License for the specific language governing permissions and
014: * limitations under the License.
015: */
016: package org.apache.commons.math.stat.descriptive.rank;
017:
018: import java.io.Serializable;
019:
020: import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
021:
022: /**
023: * Returns the minimum of the available values.
024: * <p>
025: * <ul>
026: * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
027: * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
028: * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
029: * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
030: * </ul>
031: * <p>
032: * <strong>Note that this implementation is not synchronized.</strong> If
033: * multiple threads access an instance of this class concurrently, and at least
034: * one of the threads invokes the <code>increment()</code> or
035: * <code>clear()</code> method, it must be synchronized externally.
036: *
037: * @version $Revision: 348519 $ $Date: 2005-11-23 12:12:18 -0700 (Wed, 23 Nov 2005) $
038: */
039: public class Min extends AbstractStorelessUnivariateStatistic implements
040: Serializable {
041:
042: /** Serializable version identifier */
043: private static final long serialVersionUID = -2941995784909003131L;
044:
045: /**Number of values that have been added */
046: private long n;
047:
048: /**Current value of the statistic */
049: private double value;
050:
051: /**
052: * Create a Min instance
053: */
054: public Min() {
055: n = 0;
056: value = Double.NaN;
057: }
058:
059: /**
060: * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
061: */
062: public void increment(final double d) {
063: if (d < value || Double.isNaN(value)) {
064: value = d;
065: }
066: n++;
067: }
068:
069: /**
070: * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
071: */
072: public void clear() {
073: value = Double.NaN;
074: n = 0;
075: }
076:
077: /**
078: * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
079: */
080: public double getResult() {
081: return value;
082: }
083:
084: /**
085: * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
086: */
087: public long getN() {
088: return n;
089: }
090:
091: /**
092: * Returns the minimum of the entries in the specified portion of
093: * the input array, or <code>Double.NaN</code> if the designated subarray
094: * is empty.
095: * <p>
096: * Throws <code>IllegalArgumentException</code> if the array is null or
097: * the array index parameters are not valid.
098: * <p>
099: * <ul>
100: * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
101: * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
102: * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
103: * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
104: * </ul>
105: *
106: * @param values the input array
107: * @param begin index of the first array element to include
108: * @param length the number of elements to include
109: * @return the minimum of the values or Double.NaN if length = 0
110: * @throws IllegalArgumentException if the array is null or the array index
111: * parameters are not valid
112: */
113: public double evaluate(final double[] values, final int begin,
114: final int length) {
115: double min = Double.NaN;
116: if (test(values, begin, length)) {
117: min = values[begin];
118: for (int i = begin; i < begin + length; i++) {
119: if (!Double.isNaN(values[i])) {
120: min = (min < values[i]) ? min : values[i];
121: }
122: }
123: }
124: return min;
125: }
126: }
|