Accord.Tests.Math.MatrixTest.SolveTest5 C# (CSharp) Method

        public void SolveTest5()
        {
            // Test with singular matrix
            {
                // Create a matrix. Please note that this matrix
                // is singular (i.e. not invertible), so only a 
                // least squares solution would be feasible here.

                double[,] matrix = 
                {
                    { 1, 2, 3 },
                    { 4, 5, 6 },
                    { 7, 8, 9 },
                };

                // Define a right side vector b:
                double[] rightSide = { 1, 2, 3 };

                // Solve the linear system Ax = b by finding x:
                double[] x = Matrix.Solve(matrix, rightSide, leastSquares: true);

                // The answer should be { -1/18, 2/18, 5/18 }.

                double[] expected = { -1 / 18.0, 2 / 18.0, 5 / 18.0 };
                Assert.IsTrue(matrix.IsSingular());
                Assert.IsTrue(expected.IsEqual(x, 1e-10));
            }
            {
                double[,] matrix = 
                {
                    { 1, 2, 3 },
                    { 4, 5, 6 },
                    { 7, 8, 9 },
                };

                double[,] rightSide = { { 1 }, { 2 }, { 3 } };

                Assert.IsTrue(matrix.IsSingular());

                double[,] expected = { { -1 / 18.0 }, { 2 / 18.0 }, { 5 / 18.0 } };

                double[,] actual = Matrix.Solve(matrix, rightSide, leastSquares: true);

                Assert.IsTrue(expected.IsEqual(actual, 1e-10));
            }
        }