Mercurial > hg > de.mpg.mpiwg.itgroup.digilib.plugin
view libs/commons-math-2.1/docs/apidocs/src-html/org/apache/commons/math/distribution/ZipfDistributionImpl.html @ 13:cbf34dd4d7e6
commons-math-2.1 added
| author | dwinter |
|---|---|
| date | Tue, 04 Jan 2011 10:02:07 +0100 |
| parents | |
| children |
line wrap: on
line source
<HTML> <BODY BGCOLOR="white"> <PRE> <FONT color="green">001</FONT> /*<a name="line.1"></a> <FONT color="green">002</FONT> * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a> <FONT color="green">003</FONT> * contributor license agreements. See the NOTICE file distributed with<a name="line.3"></a> <FONT color="green">004</FONT> * this work for additional information regarding copyright ownership.<a name="line.4"></a> <FONT color="green">005</FONT> * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a> <FONT color="green">006</FONT> * (the "License"); you may not use this file except in compliance with<a name="line.6"></a> <FONT color="green">007</FONT> * the License. You may obtain a copy of the License at<a name="line.7"></a> <FONT color="green">008</FONT> *<a name="line.8"></a> <FONT color="green">009</FONT> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a> <FONT color="green">010</FONT> *<a name="line.10"></a> <FONT color="green">011</FONT> * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a> <FONT color="green">012</FONT> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a> <FONT color="green">013</FONT> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a> <FONT color="green">014</FONT> * See the License for the specific language governing permissions and<a name="line.14"></a> <FONT color="green">015</FONT> * limitations under the License.<a name="line.15"></a> <FONT color="green">016</FONT> */<a name="line.16"></a> <FONT color="green">017</FONT> <a name="line.17"></a> <FONT color="green">018</FONT> package org.apache.commons.math.distribution;<a name="line.18"></a> <FONT color="green">019</FONT> <a name="line.19"></a> <FONT color="green">020</FONT> import java.io.Serializable;<a name="line.20"></a> <FONT color="green">021</FONT> <a name="line.21"></a> <FONT color="green">022</FONT> import org.apache.commons.math.MathRuntimeException;<a name="line.22"></a> <FONT color="green">023</FONT> <a name="line.23"></a> <FONT color="green">024</FONT> /**<a name="line.24"></a> <FONT color="green">025</FONT> * Implementation for the {@link ZipfDistribution}.<a name="line.25"></a> <FONT color="green">026</FONT> *<a name="line.26"></a> <FONT color="green">027</FONT> * @version $Revision: 920852 $ $Date: 2010-03-09 07:53:44 -0500 (Tue, 09 Mar 2010) $<a name="line.27"></a> <FONT color="green">028</FONT> */<a name="line.28"></a> <FONT color="green">029</FONT> public class ZipfDistributionImpl extends AbstractIntegerDistribution<a name="line.29"></a> <FONT color="green">030</FONT> implements ZipfDistribution, Serializable {<a name="line.30"></a> <FONT color="green">031</FONT> <a name="line.31"></a> <FONT color="green">032</FONT> /** Serializable version identifier. */<a name="line.32"></a> <FONT color="green">033</FONT> private static final long serialVersionUID = -140627372283420404L;<a name="line.33"></a> <FONT color="green">034</FONT> <a name="line.34"></a> <FONT color="green">035</FONT> /** Number of elements. */<a name="line.35"></a> <FONT color="green">036</FONT> private int numberOfElements;<a name="line.36"></a> <FONT color="green">037</FONT> <a name="line.37"></a> <FONT color="green">038</FONT> /** Exponent parameter of the distribution. */<a name="line.38"></a> <FONT color="green">039</FONT> private double exponent;<a name="line.39"></a> <FONT color="green">040</FONT> <a name="line.40"></a> <FONT color="green">041</FONT> /**<a name="line.41"></a> <FONT color="green">042</FONT> * Create a new Zipf distribution with the given number of elements and<a name="line.42"></a> <FONT color="green">043</FONT> * exponent. Both values must be positive; otherwise an<a name="line.43"></a> <FONT color="green">044</FONT> * <code>IllegalArgumentException</code> is thrown.<a name="line.44"></a> <FONT color="green">045</FONT> *<a name="line.45"></a> <FONT color="green">046</FONT> * @param numberOfElements the number of elements<a name="line.46"></a> <FONT color="green">047</FONT> * @param exponent the exponent<a name="line.47"></a> <FONT color="green">048</FONT> * @exception IllegalArgumentException if n &le; 0 or s &le; 0.0<a name="line.48"></a> <FONT color="green">049</FONT> */<a name="line.49"></a> <FONT color="green">050</FONT> public ZipfDistributionImpl(final int numberOfElements, final double exponent)<a name="line.50"></a> <FONT color="green">051</FONT> throws IllegalArgumentException {<a name="line.51"></a> <FONT color="green">052</FONT> setNumberOfElementsInternal(numberOfElements);<a name="line.52"></a> <FONT color="green">053</FONT> setExponentInternal(exponent);<a name="line.53"></a> <FONT color="green">054</FONT> }<a name="line.54"></a> <FONT color="green">055</FONT> <a name="line.55"></a> <FONT color="green">056</FONT> /**<a name="line.56"></a> <FONT color="green">057</FONT> * Get the number of elements (e.g. corpus size) for the distribution.<a name="line.57"></a> <FONT color="green">058</FONT> *<a name="line.58"></a> <FONT color="green">059</FONT> * @return the number of elements<a name="line.59"></a> <FONT color="green">060</FONT> */<a name="line.60"></a> <FONT color="green">061</FONT> public int getNumberOfElements() {<a name="line.61"></a> <FONT color="green">062</FONT> return numberOfElements;<a name="line.62"></a> <FONT color="green">063</FONT> }<a name="line.63"></a> <FONT color="green">064</FONT> <a name="line.64"></a> <FONT color="green">065</FONT> /**<a name="line.65"></a> <FONT color="green">066</FONT> * Set the number of elements (e.g. corpus size) for the distribution.<a name="line.66"></a> <FONT color="green">067</FONT> * The parameter value must be positive; otherwise an<a name="line.67"></a> <FONT color="green">068</FONT> * <code>IllegalArgumentException</code> is thrown.<a name="line.68"></a> <FONT color="green">069</FONT> *<a name="line.69"></a> <FONT color="green">070</FONT> * @param n the number of elements<a name="line.70"></a> <FONT color="green">071</FONT> * @exception IllegalArgumentException if n &le; 0<a name="line.71"></a> <FONT color="green">072</FONT> * @deprecated as of 2.1 (class will become immutable in 3.0)<a name="line.72"></a> <FONT color="green">073</FONT> */<a name="line.73"></a> <FONT color="green">074</FONT> @Deprecated<a name="line.74"></a> <FONT color="green">075</FONT> public void setNumberOfElements(final int n) {<a name="line.75"></a> <FONT color="green">076</FONT> setNumberOfElementsInternal(n);<a name="line.76"></a> <FONT color="green">077</FONT> }<a name="line.77"></a> <FONT color="green">078</FONT> /**<a name="line.78"></a> <FONT color="green">079</FONT> * Set the number of elements (e.g. corpus size) for the distribution.<a name="line.79"></a> <FONT color="green">080</FONT> * The parameter value must be positive; otherwise an<a name="line.80"></a> <FONT color="green">081</FONT> * <code>IllegalArgumentException</code> is thrown.<a name="line.81"></a> <FONT color="green">082</FONT> *<a name="line.82"></a> <FONT color="green">083</FONT> * @param n the number of elements<a name="line.83"></a> <FONT color="green">084</FONT> * @exception IllegalArgumentException if n &le; 0<a name="line.84"></a> <FONT color="green">085</FONT> */<a name="line.85"></a> <FONT color="green">086</FONT> private void setNumberOfElementsInternal(final int n)<a name="line.86"></a> <FONT color="green">087</FONT> throws IllegalArgumentException {<a name="line.87"></a> <FONT color="green">088</FONT> if (n <= 0) {<a name="line.88"></a> <FONT color="green">089</FONT> throw MathRuntimeException.createIllegalArgumentException(<a name="line.89"></a> <FONT color="green">090</FONT> "invalid number of elements {0} (must be positive)",<a name="line.90"></a> <FONT color="green">091</FONT> n);<a name="line.91"></a> <FONT color="green">092</FONT> }<a name="line.92"></a> <FONT color="green">093</FONT> this.numberOfElements = n;<a name="line.93"></a> <FONT color="green">094</FONT> }<a name="line.94"></a> <FONT color="green">095</FONT> <a name="line.95"></a> <FONT color="green">096</FONT> /**<a name="line.96"></a> <FONT color="green">097</FONT> * Get the exponent characterising the distribution.<a name="line.97"></a> <FONT color="green">098</FONT> *<a name="line.98"></a> <FONT color="green">099</FONT> * @return the exponent<a name="line.99"></a> <FONT color="green">100</FONT> */<a name="line.100"></a> <FONT color="green">101</FONT> public double getExponent() {<a name="line.101"></a> <FONT color="green">102</FONT> return exponent;<a name="line.102"></a> <FONT color="green">103</FONT> }<a name="line.103"></a> <FONT color="green">104</FONT> <a name="line.104"></a> <FONT color="green">105</FONT> /**<a name="line.105"></a> <FONT color="green">106</FONT> * Set the exponent characterising the distribution.<a name="line.106"></a> <FONT color="green">107</FONT> * The parameter value must be positive; otherwise an<a name="line.107"></a> <FONT color="green">108</FONT> * <code>IllegalArgumentException</code> is thrown.<a name="line.108"></a> <FONT color="green">109</FONT> *<a name="line.109"></a> <FONT color="green">110</FONT> * @param s the exponent<a name="line.110"></a> <FONT color="green">111</FONT> * @exception IllegalArgumentException if s &le; 0.0<a name="line.111"></a> <FONT color="green">112</FONT> * @deprecated as of 2.1 (class will become immutable in 3.0)<a name="line.112"></a> <FONT color="green">113</FONT> */<a name="line.113"></a> <FONT color="green">114</FONT> @Deprecated<a name="line.114"></a> <FONT color="green">115</FONT> public void setExponent(final double s) {<a name="line.115"></a> <FONT color="green">116</FONT> setExponentInternal(s);<a name="line.116"></a> <FONT color="green">117</FONT> }<a name="line.117"></a> <FONT color="green">118</FONT> /**<a name="line.118"></a> <FONT color="green">119</FONT> * Set the exponent characterising the distribution.<a name="line.119"></a> <FONT color="green">120</FONT> * The parameter value must be positive; otherwise an<a name="line.120"></a> <FONT color="green">121</FONT> * <code>IllegalArgumentException</code> is thrown.<a name="line.121"></a> <FONT color="green">122</FONT> *<a name="line.122"></a> <FONT color="green">123</FONT> * @param s the exponent<a name="line.123"></a> <FONT color="green">124</FONT> * @exception IllegalArgumentException if s &le; 0.0<a name="line.124"></a> <FONT color="green">125</FONT> */<a name="line.125"></a> <FONT color="green">126</FONT> private void setExponentInternal(final double s)<a name="line.126"></a> <FONT color="green">127</FONT> throws IllegalArgumentException {<a name="line.127"></a> <FONT color="green">128</FONT> if (s <= 0.0) {<a name="line.128"></a> <FONT color="green">129</FONT> throw MathRuntimeException.createIllegalArgumentException(<a name="line.129"></a> <FONT color="green">130</FONT> "invalid exponent {0} (must be positive)",<a name="line.130"></a> <FONT color="green">131</FONT> s);<a name="line.131"></a> <FONT color="green">132</FONT> }<a name="line.132"></a> <FONT color="green">133</FONT> this.exponent = s;<a name="line.133"></a> <FONT color="green">134</FONT> }<a name="line.134"></a> <FONT color="green">135</FONT> <a name="line.135"></a> <FONT color="green">136</FONT> /**<a name="line.136"></a> <FONT color="green">137</FONT> * The probability mass function P(X = x) for a Zipf distribution.<a name="line.137"></a> <FONT color="green">138</FONT> *<a name="line.138"></a> <FONT color="green">139</FONT> * @param x the value at which the probability density function is evaluated.<a name="line.139"></a> <FONT color="green">140</FONT> * @return the value of the probability mass function at x<a name="line.140"></a> <FONT color="green">141</FONT> */<a name="line.141"></a> <FONT color="green">142</FONT> public double probability(final int x) {<a name="line.142"></a> <FONT color="green">143</FONT> if (x <= 0 || x > numberOfElements) {<a name="line.143"></a> <FONT color="green">144</FONT> return 0.0;<a name="line.144"></a> <FONT color="green">145</FONT> }<a name="line.145"></a> <FONT color="green">146</FONT> <a name="line.146"></a> <FONT color="green">147</FONT> return (1.0 / Math.pow(x, exponent)) / generalizedHarmonic(numberOfElements, exponent);<a name="line.147"></a> <FONT color="green">148</FONT> <a name="line.148"></a> <FONT color="green">149</FONT> }<a name="line.149"></a> <FONT color="green">150</FONT> <a name="line.150"></a> <FONT color="green">151</FONT> /**<a name="line.151"></a> <FONT color="green">152</FONT> * The probability distribution function P(X <= x) for a Zipf distribution.<a name="line.152"></a> <FONT color="green">153</FONT> *<a name="line.153"></a> <FONT color="green">154</FONT> * @param x the value at which the PDF is evaluated.<a name="line.154"></a> <FONT color="green">155</FONT> * @return Zipf distribution function evaluated at x<a name="line.155"></a> <FONT color="green">156</FONT> */<a name="line.156"></a> <FONT color="green">157</FONT> @Override<a name="line.157"></a> <FONT color="green">158</FONT> public double cumulativeProbability(final int x) {<a name="line.158"></a> <FONT color="green">159</FONT> if (x <= 0) {<a name="line.159"></a> <FONT color="green">160</FONT> return 0.0;<a name="line.160"></a> <FONT color="green">161</FONT> } else if (x >= numberOfElements) {<a name="line.161"></a> <FONT color="green">162</FONT> return 1.0;<a name="line.162"></a> <FONT color="green">163</FONT> }<a name="line.163"></a> <FONT color="green">164</FONT> <a name="line.164"></a> <FONT color="green">165</FONT> return generalizedHarmonic(x, exponent) / generalizedHarmonic(numberOfElements, exponent);<a name="line.165"></a> <FONT color="green">166</FONT> <a name="line.166"></a> <FONT color="green">167</FONT> }<a name="line.167"></a> <FONT color="green">168</FONT> <a name="line.168"></a> <FONT color="green">169</FONT> /**<a name="line.169"></a> <FONT color="green">170</FONT> * Access the domain value lower bound, based on <code>p</code>, used to<a name="line.170"></a> <FONT color="green">171</FONT> * bracket a PDF root.<a name="line.171"></a> <FONT color="green">172</FONT> *<a name="line.172"></a> <FONT color="green">173</FONT> * @param p the desired probability for the critical value<a name="line.173"></a> <FONT color="green">174</FONT> * @return domain value lower bound, i.e.<a name="line.174"></a> <FONT color="green">175</FONT> * P(X &lt; <i>lower bound</i>) &lt; <code>p</code><a name="line.175"></a> <FONT color="green">176</FONT> */<a name="line.176"></a> <FONT color="green">177</FONT> @Override<a name="line.177"></a> <FONT color="green">178</FONT> protected int getDomainLowerBound(final double p) {<a name="line.178"></a> <FONT color="green">179</FONT> return 0;<a name="line.179"></a> <FONT color="green">180</FONT> }<a name="line.180"></a> <FONT color="green">181</FONT> <a name="line.181"></a> <FONT color="green">182</FONT> /**<a name="line.182"></a> <FONT color="green">183</FONT> * Access the domain value upper bound, based on <code>p</code>, used to<a name="line.183"></a> <FONT color="green">184</FONT> * bracket a PDF root.<a name="line.184"></a> <FONT color="green">185</FONT> *<a name="line.185"></a> <FONT color="green">186</FONT> * @param p the desired probability for the critical value<a name="line.186"></a> <FONT color="green">187</FONT> * @return domain value upper bound, i.e.<a name="line.187"></a> <FONT color="green">188</FONT> * P(X &lt; <i>upper bound</i>) &gt; <code>p</code><a name="line.188"></a> <FONT color="green">189</FONT> */<a name="line.189"></a> <FONT color="green">190</FONT> @Override<a name="line.190"></a> <FONT color="green">191</FONT> protected int getDomainUpperBound(final double p) {<a name="line.191"></a> <FONT color="green">192</FONT> return numberOfElements;<a name="line.192"></a> <FONT color="green">193</FONT> }<a name="line.193"></a> <FONT color="green">194</FONT> <a name="line.194"></a> <FONT color="green">195</FONT> <a name="line.195"></a> <FONT color="green">196</FONT> /**<a name="line.196"></a> <FONT color="green">197</FONT> * Calculates the Nth generalized harmonic number. See<a name="line.197"></a> <FONT color="green">198</FONT> * <a href="http://mathworld.wolfram.com/HarmonicSeries.html">Harmonic<a name="line.198"></a> <FONT color="green">199</FONT> * Series</a>.<a name="line.199"></a> <FONT color="green">200</FONT> *<a name="line.200"></a> <FONT color="green">201</FONT> * @param n the term in the series to calculate (must be &ge; 1)<a name="line.201"></a> <FONT color="green">202</FONT> * @param m the exponent; special case m == 1.0 is the harmonic series<a name="line.202"></a> <FONT color="green">203</FONT> * @return the nth generalized harmonic number<a name="line.203"></a> <FONT color="green">204</FONT> */<a name="line.204"></a> <FONT color="green">205</FONT> private double generalizedHarmonic(final int n, final double m) {<a name="line.205"></a> <FONT color="green">206</FONT> double value = 0;<a name="line.206"></a> <FONT color="green">207</FONT> for (int k = n; k > 0; --k) {<a name="line.207"></a> <FONT color="green">208</FONT> value += 1.0 / Math.pow(k, m);<a name="line.208"></a> <FONT color="green">209</FONT> }<a name="line.209"></a> <FONT color="green">210</FONT> return value;<a name="line.210"></a> <FONT color="green">211</FONT> }<a name="line.211"></a> <FONT color="green">212</FONT> <a name="line.212"></a> <FONT color="green">213</FONT> }<a name="line.213"></a> </PRE> </BODY> </HTML>