Python/matrix/matrix_multiplication_addition.py
RayCurse 441b82a95f More matrix algorithms (#745)
* added matrix minor

* added matrix determinant

* added inverse,scalar multiply, identity, transpose
2019-03-28 01:50:43 +08:00

76 lines
2.1 KiB
Python

def add(matrix_a, matrix_b):
rows = len(matrix_a)
columns = len(matrix_a[0])
matrix_c = []
for i in range(rows):
list_1 = []
for j in range(columns):
val = matrix_a[i][j] + matrix_b[i][j]
list_1.append(val)
matrix_c.append(list_1)
return matrix_c
def scalarMultiply(matrix , n):
return [[x * n for x in row] for row in matrix]
def multiply(matrix_a, matrix_b):
matrix_c = []
n = len(matrix_a)
for i in range(n):
list_1 = []
for j in range(n):
val = 0
for k in range(n):
val = val + matrix_a[i][k] * matrix_b[k][j]
list_1.append(val)
matrix_c.append(list_1)
return matrix_c
def identity(n):
return [[int(row == column) for column in range(n)] for row in range(n)]
def transpose(matrix):
return map(list , zip(*matrix))
def minor(matrix, row, column):
minor = matrix[:row] + matrix[row + 1:]
minor = [row[:column] + row[column + 1:] for row in minor]
return minor
def determinant(matrix):
if len(matrix) == 1: return matrix[0][0]
res = 0
for x in range(len(matrix)):
res += matrix[0][x] * determinant(minor(matrix , 0 , x)) * (-1) ** x
return res
def inverse(matrix):
det = determinant(matrix)
if det == 0: return None
matrixMinor = [[] for _ in range(len(matrix))]
for i in range(len(matrix)):
for j in range(len(matrix)):
matrixMinor[i].append(determinant(minor(matrix , i , j)))
cofactors = [[x * (-1) ** (row + col) for col, x in enumerate(matrixMinor[row])] for row in range(len(matrix))]
adjugate = transpose(cofactors)
return scalarMultiply(adjugate , 1/det)
def main():
matrix_a = [[12, 10], [3, 9]]
matrix_b = [[3, 4], [7, 4]]
matrix_c = [[11, 12, 13, 14], [21, 22, 23, 24], [31, 32, 33, 34], [41, 42, 43, 44]]
matrix_d = [[3, 0, 2], [2, 0, -2], [0, 1, 1]]
print(add(matrix_a, matrix_b))
print(multiply(matrix_a, matrix_b))
print(identity(5))
print(minor(matrix_c , 1 , 2))
print(determinant(matrix_b))
print(inverse(matrix_d))
if __name__ == '__main__':
main()