com.golemgame.util.LinearInterpolator.java Source code

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Here is the source code for com.golemgame.util.LinearInterpolator.java

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/*******************************************************************************
 * Copyright 2008, 2009, 2010 Sam Bayless.
 * 
 *     This file is part of Golems.
 * 
 *     Golems is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 * 
 *     Golems is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 * 
 *     You should have received a copy of the GNU General Public License
 *     along with Golems. If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package com.golemgame.util;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;

import org.apache.commons.math.analysis.UnivariateRealFunction;
import org.apache.commons.math.analysis.UnivariateRealInterpolator;

public class LinearInterpolator implements UnivariateRealInterpolator, Serializable {
    private static final long serialVersionUID = 1;
    private static final LinearInterpolator instance = new LinearInterpolator();

    public static LinearInterpolator getInstance() {
        return instance;
    }

    public LinearInterpolationFunction interpolate(double[] arg0, double[] arg1) {
        return new LinearInterpolationFunction(arg0, arg1);
    }

    public static class LinearInterpolationFunction
            implements UnivariateRealFunction, KnottedFunction, Serializable {
        private static final long serialVersionUID = 1;
        double[] x;
        double[] y;

        public LinearInterpolationFunction(double[] x, double[] y) {
            this.x = x;
            this.y = y;
            //these tests are no longer necessary (moved into golems validation), but they dont hurt.
            if (y != null) {
                for (int i = 0; i < y.length; i++) {
                    if (Double.isInfinite(y[i]) || Double.isNaN(y[i]))
                        this.y[i] = 0f;

                }
            }
            if (x != null) {
                for (int i = 0; i < x.length; i++) {
                    if (Double.isInfinite(x[i]) || Double.isNaN(x[i]))
                        this.x[i] = 0f;

                }
            }
        }

        public boolean isEmpty() {
            return (x == null || x.length < 2 || y == null || y.length < 2);
        }

        public double value(double arg0) {

            int pos = Arrays.binarySearch(x, arg0);
            if (pos == -1) {
                pos = 0;
            } else if (pos < 0) {
                pos = -pos - 2;
            }
            pos++;
            if (pos >= x.length) {
                pos = x.length - 1;
            }
            double y0 = y[pos - 1];
            double y1 = y[pos];
            double x0 = x[pos - 1];
            double x1 = x[pos];

            if (x0 == x1)
                x1 += Double.MIN_VALUE;
            return y0 + (arg0 - x0) * ((y1 - y0) / (x1 - x0));

        }

        public double[] getXKnots() {
            return x;
        }

        public double[] getYKnots() {
            return y;
        }

        public boolean isKnotted() {
            return true;
        }

        public int count() {
            return x == null ? 0 : x.length;
        }

        private transient ArrayList<Double> xList = null;
        private transient ArrayList<Double> yList = null;

    }

}