public static double interpolate(double[][] matrix) {
        return interpolate(matrix, 1.0E-6);
    }
@Test
    public void testInterpolate() {
        System.out.println("interpolate");
        double[][] matrix = {{0, Double.NaN}, {1, 2}};
        double error = LaplaceInterpolation.interpolate(matrix);
        assertEquals(0, matrix[0][0], 1E-7);
        assertEquals(1, matrix[1][0], 1E-7);
        assertEquals(2, matrix[1][1], 1E-7);
        assertEquals(1, matrix[0][1], 1E-7);
        assertTrue(error < 1E-6);
    }