Vector Projection between two double List - Java java.lang

Java examples for java.lang:double Array

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Description

Vector Projection between two double List

Demo Code

/*// www  .  jav a 2 s . c  o m
 * VectorHelpers.java
 * Copyright (C) 2014 Amin Bandali <me@aminb.org>
 *
 * MATHTools 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.
 *
 * MATHTools 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 this program. If not, see <http://www.gnu.org/licenses/>.
 */
//package com.java2s;
import java.util.List;

public class Main {
    public static double[] calcVectorProjection(List<Double> in1,
            List<Double> in2) {
        double b, x, y, scalarProjection;
        double[] res;
        scalarProjection = calcScalarProjection(in1, in2);

        switch (in1.size()) {
        case 2:
            b = getMagnitude(in2.get(0), in2.get(1));
            x = (scalarProjection / b) * in2.get(0);
            y = (scalarProjection / b) * in2.get(1);
            res = new double[2];
            res[0] = x;
            res[1] = y;
            return res;
        case 3:
            b = getMagnitude(in2.get(0), in2.get(1), in2.get(2));
            x = (scalarProjection / b) * in2.get(0);
            y = (scalarProjection / b) * in2.get(1);
            double z = (scalarProjection / b) * in2.get(2);
            res = new double[3];
            res[0] = x;
            res[1] = y;
            res[2] = z;
            return res;
        default:
            double[] no = { 0, 0 };
            return no;
        }
    }

    public static double calcScalarProjection(List<Double> in1,
            List<Double> in2) {
        double dotProduct, b;
        dotProduct = calcDotProduct(in1, in2);

        switch (in1.size()) {
        case 2:
            b = getMagnitude(in2.get(0), in2.get(1));
            return Math.abs(dotProduct / b);
        case 3:
            b = getMagnitude(in2.get(0), in2.get(1), in2.get(2));
            return Math.abs(dotProduct / b);
        default:
            return 0;
        }
    }

    public static final double getMagnitude(double a, double b) {
        return Math.sqrt(a * a + b * b);
    }

    public static final double getMagnitude(double a, double b, double c) {
        return Math.sqrt(a * a + b * b + c * c);
    }

    public static double calcDotProduct(List<Double> in1, List<Double> in2) {
        Double dotProduct = 0d;

        for (int i = 0; i < in1.size(); i++) {
            dotProduct += in1.get(i) * in2.get(i);
        }

        return dotProduct;
    }
}

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