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1 /** Copyright (C) 2017 by Bundesanstalt für Gewässerkunde |
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2 * Software engineering by |
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3 * Björnsen Beratende Ingenieure GmbH |
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4 * Dr. Schumacher Ingenieurbüro für Wasser und Umwelt |
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5 * |
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6 * This file is Free Software under the GNU AGPL (>=v3) |
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7 * and comes with ABSOLUTELY NO WARRANTY! Check out the |
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8 * documentation coming with Dive4Elements River for details. |
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9 */ |
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10 package org.dive4elements.river.artifacts.math.fitting; |
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11 |
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12 /** |
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13 * @author Domenico Nardi Tironi |
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14 * |
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15 */ |
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16 /* |
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17 * Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde |
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18 * Software engineering by Intevation GmbH |
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19 * This file is Free Software under the GNU AGPL (>=v3) |
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20 * and comes with ABSOLUTELY NO WARRANTY! Check out the |
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21 * documentation coming with Dive4Elements River for details. |
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22 */ |
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23 |
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24 public abstract class AbstractLogLinear extends Function { |
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25 public static final Derivative DERIVATIVE = new Derivative("W'(Q) = a*m/(m*Q + b)") { |
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26 |
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27 @Override |
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28 public org.dive4elements.river.artifacts.math.Function instantiate(final double[] parameters) { |
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29 final double a = parameters[0]; |
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30 final double m = parameters[1]; |
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31 final double b = parameters[2]; |
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32 |
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33 return new org.dive4elements.river.artifacts.math.Function() { |
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34 @Override |
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35 public double value(final double Q) { |
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36 return a * m / (m * Q + b); |
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37 } |
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38 }; |
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39 } |
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40 }; |
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41 |
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42 public AbstractLogLinear(final String name, final String description) { |
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43 super(name, description, new String[] { "a", "m", "b" }); |
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44 } |
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45 |
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46 @Override |
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47 public final double value(final double x, final double[] parameters) { |
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48 return parameters[0] * Math.log(parameters[1] * x + parameters[2]); |
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49 } |
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50 |
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51 @Override |
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52 public double[] gradient(final double x, final double[] parameters) { |
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53 final double a = parameters[0]; |
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54 final double m = parameters[1]; |
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55 final double b = parameters[2]; |
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56 |
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57 final double lin = m * x + b; |
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58 |
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59 return new double[] { Math.log(lin), a * x / lin, a / lin }; |
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60 } |
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61 |
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62 @Override |
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63 public final Derivative getDerivative() { |
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64 return DERIVATIVE; |
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65 } |
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66 |
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67 @Override |
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68 public Function getInverse() { |
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69 return InvLogLinear.INSTANCE; |
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70 } |
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71 } |
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72 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |
