Routine Name: matrixSub

Author: Christopher Johnson

Language: C++11. Tested with g++ compiler.

Declared in “matrix.h”

Description/Purpose: Computes the difference of two matrices.

Input: Matrix a and Matrix b, where Matrix is a typedef of std::vector<std::vector<double>>.

Output: Returns a Matrix, of size equal to the input matrices.

Usage/Example:

Two Matrices must first be defined, and then the method may be called.

Matrix a(5, Vector{-2,-1,0,1,2}); \\Creates a vector with 5 rows of [-2,-1,0,-1,-2]
Matrix b(5, Vector(5,1)); \\5*5 matrix of all ones
std::cout << "The matrix difference A + B is \n";
printMatrix(matrixSub(a,b));

Output from the lines above:

The matrix difference A + B is
[[-3,-2,-1,0,1],
 [-3,-2,-1,0,1],
 [-3,-2,-1,0,1],
 [-3,-2,-1,0,1],
 [-3,-2,-1,0,1]]

Implementation/Code: The following is the code for matrixSub(a,b)

Matrix matrixSub(Matrix a, Matrix b)
{
    int n = a.size();
    int m = a[0].size();
    Matrix sol (m, Vector(n,0));

    for (int i=0;i<n;++i)
        for (int j=0;j<m;++j)
            sol[i][j] = a[i][j] - b[i][j];

    return sol;
}

Last Modified: October/2017