def test_raise_exception_when_inverse_of_a_noninvertible_matrix():
A = Matrix(-4, 2, -2, -3,
9, 6, 2, 6,
0, -5, 1, -5,
0, 0, 0, 0)
assert not A.is_invertible()
with pytest.raises(NonInvertibleMatrixError):
A.inverse()
def test_calculating_the_inverse_of_a_third_matrix():
# Given
A = Matrix(9, 3, 0, 9,
-5, -2, -6, -3,
-4, 9, 6, 4,
-7, 6, 6, 2)
# Then
assert A.inverse() == Matrix(-0.04074, -0.07778, 0.14444, -0.22222,
-0.07778, 0.03333, 0.36667, -0.33333,
-0.02901, -0.14630, -0.10926, 0.12963,
0.17778, 0.06667, -0.26667, 0.33333)
def test_calculating_the_inverse_of_another_matrix():
# Given
A = Matrix(8, -5, 9, 2,
7, 5, 6, 1,
-6, 0, 9, 6,
-3, 0, -9, -4)
# Then
assert A.inverse() == Matrix(-0.15385, -0.15385, -0.28205, -0.53846,
-0.07692, 0.12308, 0.02564, 0.03077,
0.35897, 0.35897, 0.43590, 0.92308,
-0.69231, -0.69231, -0.76923, -1.92308)
def test_multiplying_a_product_by_its_inverse():
# Given
A = Matrix(3, -9, 7, 3,
3, -8, 2, -9,
-4, 4, 4, 1,
-6, 5, -1, 1)
B = Matrix(8, 2, 2, 2,
3, -1, 7, 0,
7, 0, 5, 4,
6, -2, 0, 5)
C = A * B
# Then
assert C * B.inverse() == A
def test_calculating_the_inverse_of_a_matrix():
# Given
A = Matrix(-5, 2, 6, -8,
1, -5, 1, 8,
7, 7, -6, -7,
1, -3, 7, 4)
B = A.inverse()
# Then
assert A.determinant() == 532
assert A.cofactor(2, 3) == -160
assert equal(B.at(3, 2), -160/532)
assert A.cofactor(3, 2) == 105
assert equal(B.at(2, 3), 105/532)
assert B == Matrix(0.21805, 0.45113, 0.24060, -0.04511,
-0.80827, -1.45677, -0.44361, 0.52068,
-0.07895, -0.22368, -0.05263, 0.19737,
-0.52256, -0.81391, -0.30075, 0.30639)
