Java Matrix Product matrixProduct(double[][] A, double[][] B)

Description

Return the matrix product A x B

License

Open Source License

Parameter

Parameter	Description
A	mxn matrix
B	nxq matrix

Return

mxq matrix product of A and B

Declaration

public static double[][] matrixProduct(double[][] A, double[][] B) throws Exception 

Method Source Code

//package com.java2s;
/*//w ww.j  a v  a2  s  .co  m
 *  Java Information Dynamics Toolkit (JIDT)
 *  Copyright (C) 2012, Joseph T. Lizier
 *  
 *  This program 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.
 *  
 *  This program 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/>.
 */

public class Main {
    /**
     * Return the matrix product A x B
     * 
     * @param A mxn matrix
     * @param B nxq matrix
     * @return mxq matrix product of A and B
     */
    public static double[][] matrixProduct(double[][] A, double[][] B) throws Exception {
        if (A[0].length != B.length) {
            throw new Exception("Number of columns of a " + A[0].length + " does not match the number of rows of b "
                    + B.length);
        }
        double[][] result = new double[A.length][B[0].length];
        for (int r = 0; r < result.length; r++) {
            for (int c = 0; c < result[r].length; c++) {
                result[r][c] = 0;
                for (int k = 0; k < A[r].length; k++) {
                    result[r][c] += A[r][k] * B[k][c];
                }
            }
        }
        return result;
    }

    /**
     * Return the matrix product v A
     *  (i.e. a left multiplication of the 1xn vector and the nxm matrix A)
     * 
     * @param v a 1xn vector
     * @param A an nxm matrix
     * @return a 1xm vector output
     */
    public static double[] matrixProduct(double[] v, double[][] A) throws Exception {
        if (v.length != A.length) {
            throw new Exception(
                    "Number of entries of v " + v.length + " does not match the number of rows of A " + A.length);
        }
        // Result length is the number of columns of A
        double[] result = new double[A[0].length];
        for (int c = 0; c < result.length; c++) {
            result[c] = 0;
            for (int r = 0; r < v.length; r++) {
                result[c] += v[r] * A[r][c];
            }
        }
        return result;
    }

    /**
     * Return the matrix product A v
     *  (i.e. a right multiplication of the nxm matrix A and the 1xn vector)
     * 
     * @param A an mxn matrix
     * @param v a nx1 vector
     * @return a mx1 vector output
     */
    public static double[] matrixProduct(double[][] A, double[] v) throws Exception {
        if (v.length != A[0].length) {
            throw new Exception("Number of entries of v " + v.length + " does not match the number of columns of A "
                    + A[0].length);
        }
        // Result length is the number of rows of A
        double[] result = new double[A.length];
        for (int r = 0; r < result.length; r++) {
            result[r] = 0;
            for (int c = 0; c < v.length; c++) {
                result[r] += A[r][c] * v[c];
            }
        }
        return result;
    }
}

Related

1. matrix_vector_product(double[][] a, double[] v)
2. matrixInnerProduct(int M, int N, double m1[][], double m2[][])
3. matrixProduct(double[][] m, double[][] n)
4. matrixProduct(double[][] x, double[] y)
5. matrixProductVDVT(final double[][] V, final double[] d, final double[][] A, int n)
6. product(final T[][] args)