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1 <HTML>
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2 <BODY BGCOLOR="white">
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3 <PRE>
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4 <FONT color="green">001</FONT> /*<a name="line.1"></a>
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5 <FONT color="green">002</FONT> * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a>
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6 <FONT color="green">003</FONT> * contributor license agreements. See the NOTICE file distributed with<a name="line.3"></a>
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7 <FONT color="green">004</FONT> * this work for additional information regarding copyright ownership.<a name="line.4"></a>
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8 <FONT color="green">005</FONT> * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a>
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9 <FONT color="green">006</FONT> * (the "License"); you may not use this file except in compliance with<a name="line.6"></a>
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10 <FONT color="green">007</FONT> * the License. You may obtain a copy of the License at<a name="line.7"></a>
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11 <FONT color="green">008</FONT> *<a name="line.8"></a>
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12 <FONT color="green">009</FONT> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a>
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13 <FONT color="green">010</FONT> *<a name="line.10"></a>
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14 <FONT color="green">011</FONT> * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a>
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15 <FONT color="green">012</FONT> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a>
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16 <FONT color="green">013</FONT> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a>
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17 <FONT color="green">014</FONT> * See the License for the specific language governing permissions and<a name="line.14"></a>
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18 <FONT color="green">015</FONT> * limitations under the License.<a name="line.15"></a>
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19 <FONT color="green">016</FONT> */<a name="line.16"></a>
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20 <FONT color="green">017</FONT> <a name="line.17"></a>
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21 <FONT color="green">018</FONT> package org.apache.commons.math.optimization.fitting;<a name="line.18"></a>
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22 <FONT color="green">019</FONT> <a name="line.19"></a>
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23 <FONT color="green">020</FONT> import org.apache.commons.math.FunctionEvaluationException;<a name="line.20"></a>
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24 <FONT color="green">021</FONT> import org.apache.commons.math.MathRuntimeException;<a name="line.21"></a>
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25 <FONT color="green">022</FONT> import org.apache.commons.math.analysis.polynomials.PolynomialFunction;<a name="line.22"></a>
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26 <FONT color="green">023</FONT> import org.apache.commons.math.optimization.DifferentiableMultivariateVectorialOptimizer;<a name="line.23"></a>
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27 <FONT color="green">024</FONT> import org.apache.commons.math.optimization.OptimizationException;<a name="line.24"></a>
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28 <FONT color="green">025</FONT> <a name="line.25"></a>
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29 <FONT color="green">026</FONT> /** This class implements a curve fitting specialized for polynomials.<a name="line.26"></a>
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30 <FONT color="green">027</FONT> * <p>Polynomial fitting is a very simple case of curve fitting. The<a name="line.27"></a>
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31 <FONT color="green">028</FONT> * estimated coefficients are the polynomial coefficients. They are<a name="line.28"></a>
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32 <FONT color="green">029</FONT> * searched by a least square estimator.</p><a name="line.29"></a>
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33 <FONT color="green">030</FONT> * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $<a name="line.30"></a>
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34 <FONT color="green">031</FONT> * @since 2.0<a name="line.31"></a>
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35 <FONT color="green">032</FONT> */<a name="line.32"></a>
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36 <FONT color="green">033</FONT> <a name="line.33"></a>
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37 <FONT color="green">034</FONT> public class PolynomialFitter {<a name="line.34"></a>
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38 <FONT color="green">035</FONT> <a name="line.35"></a>
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39 <FONT color="green">036</FONT> /** Fitter for the coefficients. */<a name="line.36"></a>
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40 <FONT color="green">037</FONT> private final CurveFitter fitter;<a name="line.37"></a>
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41 <FONT color="green">038</FONT> <a name="line.38"></a>
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42 <FONT color="green">039</FONT> /** Polynomial degree. */<a name="line.39"></a>
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43 <FONT color="green">040</FONT> private final int degree;<a name="line.40"></a>
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44 <FONT color="green">041</FONT> <a name="line.41"></a>
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45 <FONT color="green">042</FONT> /** Simple constructor.<a name="line.42"></a>
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46 <FONT color="green">043</FONT> * <p>The polynomial fitter built this way are complete polynomials,<a name="line.43"></a>
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47 <FONT color="green">044</FONT> * ie. a n-degree polynomial has n+1 coefficients.</p><a name="line.44"></a>
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48 <FONT color="green">045</FONT> * @param degree maximal degree of the polynomial<a name="line.45"></a>
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49 <FONT color="green">046</FONT> * @param optimizer optimizer to use for the fitting<a name="line.46"></a>
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50 <FONT color="green">047</FONT> */<a name="line.47"></a>
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51 <FONT color="green">048</FONT> public PolynomialFitter(int degree, final DifferentiableMultivariateVectorialOptimizer optimizer) {<a name="line.48"></a>
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52 <FONT color="green">049</FONT> this.fitter = new CurveFitter(optimizer);<a name="line.49"></a>
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53 <FONT color="green">050</FONT> this.degree = degree;<a name="line.50"></a>
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54 <FONT color="green">051</FONT> }<a name="line.51"></a>
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55 <FONT color="green">052</FONT> <a name="line.52"></a>
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56 <FONT color="green">053</FONT> /** Add an observed weighted (x,y) point to the sample.<a name="line.53"></a>
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57 <FONT color="green">054</FONT> * @param weight weight of the observed point in the fit<a name="line.54"></a>
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58 <FONT color="green">055</FONT> * @param x abscissa of the point<a name="line.55"></a>
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59 <FONT color="green">056</FONT> * @param y observed value of the point at x, after fitting we should<a name="line.56"></a>
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60 <FONT color="green">057</FONT> * have P(x) as close as possible to this value<a name="line.57"></a>
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61 <FONT color="green">058</FONT> */<a name="line.58"></a>
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62 <FONT color="green">059</FONT> public void addObservedPoint(double weight, double x, double y) {<a name="line.59"></a>
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63 <FONT color="green">060</FONT> fitter.addObservedPoint(weight, x, y);<a name="line.60"></a>
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64 <FONT color="green">061</FONT> }<a name="line.61"></a>
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65 <FONT color="green">062</FONT> <a name="line.62"></a>
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66 <FONT color="green">063</FONT> /** Get the polynomial fitting the weighted (x, y) points.<a name="line.63"></a>
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67 <FONT color="green">064</FONT> * @return polynomial function best fitting the observed points<a name="line.64"></a>
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68 <FONT color="green">065</FONT> * @exception OptimizationException if the algorithm failed to converge<a name="line.65"></a>
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69 <FONT color="green">066</FONT> */<a name="line.66"></a>
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70 <FONT color="green">067</FONT> public PolynomialFunction fit()<a name="line.67"></a>
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71 <FONT color="green">068</FONT> throws OptimizationException {<a name="line.68"></a>
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72 <FONT color="green">069</FONT> try {<a name="line.69"></a>
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73 <FONT color="green">070</FONT> return new PolynomialFunction(fitter.fit(new ParametricPolynomial(), new double[degree + 1]));<a name="line.70"></a>
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74 <FONT color="green">071</FONT> } catch (FunctionEvaluationException fee) {<a name="line.71"></a>
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75 <FONT color="green">072</FONT> // this should never happen<a name="line.72"></a>
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76 <FONT color="green">073</FONT> throw MathRuntimeException.createInternalError(fee);<a name="line.73"></a>
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77 <FONT color="green">074</FONT> }<a name="line.74"></a>
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78 <FONT color="green">075</FONT> }<a name="line.75"></a>
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79 <FONT color="green">076</FONT> <a name="line.76"></a>
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80 <FONT color="green">077</FONT> /** Dedicated parametric polynomial class. */<a name="line.77"></a>
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81 <FONT color="green">078</FONT> private static class ParametricPolynomial implements ParametricRealFunction {<a name="line.78"></a>
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82 <FONT color="green">079</FONT> <a name="line.79"></a>
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83 <FONT color="green">080</FONT> /** {@inheritDoc} */<a name="line.80"></a>
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84 <FONT color="green">081</FONT> public double[] gradient(double x, double[] parameters)<a name="line.81"></a>
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85 <FONT color="green">082</FONT> throws FunctionEvaluationException {<a name="line.82"></a>
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86 <FONT color="green">083</FONT> final double[] gradient = new double[parameters.length];<a name="line.83"></a>
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87 <FONT color="green">084</FONT> double xn = 1.0;<a name="line.84"></a>
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88 <FONT color="green">085</FONT> for (int i = 0; i < parameters.length; ++i) {<a name="line.85"></a>
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89 <FONT color="green">086</FONT> gradient[i] = xn;<a name="line.86"></a>
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90 <FONT color="green">087</FONT> xn *= x;<a name="line.87"></a>
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91 <FONT color="green">088</FONT> }<a name="line.88"></a>
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92 <FONT color="green">089</FONT> return gradient;<a name="line.89"></a>
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93 <FONT color="green">090</FONT> }<a name="line.90"></a>
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94 <FONT color="green">091</FONT> <a name="line.91"></a>
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95 <FONT color="green">092</FONT> /** {@inheritDoc} */<a name="line.92"></a>
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96 <FONT color="green">093</FONT> public double value(final double x, final double[] parameters) {<a name="line.93"></a>
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97 <FONT color="green">094</FONT> double y = 0;<a name="line.94"></a>
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98 <FONT color="green">095</FONT> for (int i = parameters.length - 1; i >= 0; --i) {<a name="line.95"></a>
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99 <FONT color="green">096</FONT> y = y * x + parameters[i];<a name="line.96"></a>
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100 <FONT color="green">097</FONT> }<a name="line.97"></a>
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101 <FONT color="green">098</FONT> return y;<a name="line.98"></a>
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102 <FONT color="green">099</FONT> }<a name="line.99"></a>
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103 <FONT color="green">100</FONT> <a name="line.100"></a>
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104 <FONT color="green">101</FONT> }<a name="line.101"></a>
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105 <FONT color="green">102</FONT> <a name="line.102"></a>
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106 <FONT color="green">103</FONT> }<a name="line.103"></a>
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167 </PRE>
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168 </BODY>
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169 </HTML>
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