diff --git a/matrix/matrix_class.py b/matrix/matrix_class.py new file mode 100644 index 000000000..2cd43fc9c --- /dev/null +++ b/matrix/matrix_class.py @@ -0,0 +1,364 @@ +# An OOP aproach to representing and manipulating matrices + + +class Matrix: + """ + Matrix object generated from a 2D array where each element is an array representing a row. + Rows can contain type int or float. + Common operations and information available. + >>> rows = [ + ... [1, 2, 3], + ... [4, 5, 6], + ... [7, 8, 9] + ... ] + >>> matrix = Matrix(rows) + >>> print(matrix) + [[1. 2. 3.] + [4. 5. 6.] + [7. 8. 9.]] + + Matrix rows and columns are available as 2D arrays + >>> print(matrix.rows) + [[1, 2, 3], [4, 5, 6], [7, 8, 9]] + >>> print(matrix.columns()) + [[1, 4, 7], [2, 5, 8], [3, 6, 9]] + + Order is returned as a tuple + >>> matrix.order + (3, 3) + + Squareness and invertability are represented as bool + >>> matrix.is_square + True + >>> matrix.is_invertable() + False + + Identity, Minors, Cofactors and Adjugate are returned as Matrices. Inverse can be a Matrix or Nonetype + >>> print(matrix.identity()) + [[1. 0. 0.] + [0. 1. 0.] + [0. 0. 1.]] + >>> print(matrix.minors()) + [[-3. -6. -3.] + [-6. -12. -6.] + [-3. -6. -3.]] + >>> print(matrix.cofactors()) + [[-3. 6. -3.] + [6. -12. 6.] + [-3. 6. -3.]] + >>> print(matrix.adjugate()) # won't be apparent due to the nature of the cofactor matrix + [[-3. 6. -3.] + [6. -12. 6.] + [-3. 6. -3.]] + >>> print(matrix.inverse()) + None + + Determinant is an int, float, or Nonetype + >>> matrix.determinant() + 0 + + Negation, scalar multiplication, addition, subtraction, multiplication and exponentiation are available and all return a Matrix + >>> print(-matrix) + [[-1. -2. -3.] + [-4. -5. -6.] + [-7. -8. -9.]] + >>> matrix2 = matrix * 3 + >>> print(matrix2) + [[3. 6. 9.] + [12. 15. 18.] + [21. 24. 27.]] + >>> print(matrix + matrix2) + [[4. 8. 12.] + [16. 20. 24.] + [28. 32. 36.]] + >>> print(matrix - matrix2) + [[-2. -4. -6.] + [-8. -10. -12.] + [-14. -16. -18.]] + >>> print(matrix ** 3) + [[468. 576. 684.] + [1062. 1305. 1548.] + [1656. 2034. 2412.]] + + Matrices can also be modified + >>> matrix.add_row([10, 11, 12]) + >>> print(matrix) + [[1. 2. 3.] + [4. 5. 6.] + [7. 8. 9.] + [10. 11. 12.]] + >>> matrix2.add_column([8, 16, 32]) + >>> print(matrix2) + [[3. 6. 9. 8.] + [12. 15. 18. 16.] + [21. 24. 27. 32.]] + >>> print(matrix * matrix2) + [[90. 108. 126. 136.] + [198. 243. 288. 304.] + [306. 378. 450. 472.] + [414. 513. 612. 640.]] + + """ + + def __init__(self, rows): + error = TypeError( + "Matrices must be formed from a list of zero or more lists containing at least one and the same number of values, \ + each of which must be of type int or float" + ) + if len(rows) != 0: + cols = len(rows[0]) + if cols == 0: + raise error + for row in rows: + if not len(row) == cols: + raise error + for value in row: + if not isinstance(value, (int, float)): + raise error + self.rows = rows + else: + self.rows = [] + + # MATRIX INFORMATION + def columns(self): + return [[row[i] for row in self.rows] for i in range(len(self.rows[0]))] + + @property + def num_rows(self): + return len(self.rows) + + @property + def num_columns(self): + return len(self.rows[0]) + + @property + def order(self): + return (self.num_rows, self.num_columns) + + @property + def is_square(self): + if self.order[0] == self.order[1]: + return True + return False + + def identity(self): + values = [ + [0 if column_num != row_num else 1 for column_num in range(self.num_rows)] + for row_num in range(self.num_rows) + ] + return Matrix(values) + + def determinant(self): + if not self.is_square: + return None + if self.order == (0, 0): + return 1 + if self.order == (1, 1): + return self.rows[0][0] + if self.order == (2, 2): + return (self.rows[0][0] * self.rows[1][1]) - ( + self.rows[0][1] * self.rows[1][0] + ) + else: + return sum( + [ + self.rows[0][column] * self.cofactors().rows[0][column] + for column in range(self.num_columns) + ] + ) + + def is_invertable(self): + if self.determinant(): + return True + return False + + def get_minor(self, row, column): + values = [ + [ + self.rows[other_row][other_column] + for other_column in range(self.num_columns) + if other_column != column + ] + for other_row in range(self.num_rows) + if other_row != row + ] + return Matrix(values).determinant() + + def get_cofactor(self, row, column): + if (row + column) % 2 == 0: + return self.get_minor(row, column) + return -1 * self.get_minor(row, column) + + def minors(self): + return Matrix( + [ + [self.get_minor(row, column) for column in range(self.num_columns)] + for row in range(self.num_rows) + ] + ) + + def cofactors(self): + return Matrix( + [ + [ + self.minors().rows[row][column] + if (row + column) % 2 == 0 + else self.minors().rows[row][column] * -1 + for column in range(self.minors().num_columns) + ] + for row in range(self.minors().num_rows) + ] + ) + + def adjugate(self): + values = [ + [self.cofactors().rows[column][row] for column in range(self.num_columns)] + for row in range(self.num_rows) + ] + return Matrix(values) + + def inverse(self): + if not self.is_invertable(): + return None + return self.adjugate() * (1 / self.determinant()) + + def __repr__(self): + return str(self.rows) + + def __str__(self): + if self.num_rows == 0: + return "[]" + if self.num_rows == 1: + return "[[" + ". ".join(self.rows[0]) + "]]" + return ( + "[" + + "\n ".join( + [ + "[" + ". ".join([str(value) for value in row]) + ".]" + for row in self.rows + ] + ) + + "]" + ) + + # MATRIX MANIPULATION + def add_row(self, row, position=None): + type_error = TypeError("Row must be a list containing all ints and/or floats") + if not isinstance(row, list): + raise type_error + for value in row: + if not isinstance(value, (int, float)): + raise type_error + if len(row) != self.num_columns: + raise ValueError( + "Row must be equal in length to the other rows in the matrix" + ) + if position is None: + self.rows.append(row) + else: + self.rows = self.rows[0:position] + [row] + self.rows[position:] + + def add_column(self, column, position=None): + type_error = TypeError( + "Column must be a list containing all ints and/or floats" + ) + if not isinstance(column, list): + raise type_error + for value in column: + if not isinstance(value, (int, float)): + raise type_error + if len(column) != self.num_rows: + raise ValueError( + "Column must be equal in length to the other columns in the matrix" + ) + if position is None: + self.rows = [self.rows[i] + [column[i]] for i in range(self.num_rows)] + else: + self.rows = [ + self.rows[i][0:position] + [column[i]] + self.rows[i][position:] + for i in range(self.num_rows) + ] + + # MATRIX OPERATIONS + def __eq__(self, other): + if not isinstance(other, Matrix): + raise TypeError("A Matrix can only be compared with another Matrix") + if self.rows == other.rows: + return True + return False + + def __ne__(self, other): + if self == other: + return False + return True + + def __neg__(self): + return self * -1 + + def __add__(self, other): + if self.order != other.order: + raise ValueError("Addition requires matrices of the same order") + return Matrix( + [ + [self.rows[i][j] + other.rows[i][j] for j in range(self.num_columns)] + for i in range(self.num_rows) + ] + ) + + def __sub__(self, other): + if self.order != other.order: + raise ValueError("Subtraction requires matrices of the same order") + return Matrix( + [ + [self.rows[i][j] - other.rows[i][j] for j in range(self.num_columns)] + for i in range(self.num_rows) + ] + ) + + def __mul__(self, other): + if not isinstance(other, (int, float, Matrix)): + raise TypeError( + "A Matrix can only be multiplied by an int, float, or another matrix" + ) + if type(other) in (int, float): + return Matrix([[element * other for element in row] for row in self.rows]) + if type(other) is Matrix: + if self.num_columns != other.num_rows: + raise ValueError( + "The number of columns in the first matrix must be equal to the number of rows in the second" + ) + return Matrix( + [ + [Matrix.dot_product(row, column) for column in other.columns()] + for row in self.rows + ] + ) + + def __pow__(self, other): + if not isinstance(other, int): + raise TypeError("A Matrix can only be raised to the power of an int") + if not self.is_square: + raise ValueError("Only square matrices can be raised to a power") + if other == 0: + return self.identity() + if other < 0: + if self.is_invertable: + return self.inverse() ** (-other) + raise ValueError( + "Only invertable matrices can be raised to a negative power" + ) + result = self + for i in range(other - 1): + result *= self + return result + + @classmethod + def dot_product(cls, row, column): + return sum([row[i] * column[i] for i in range(len(row))]) + + +if __name__ == "__main__": + import doctest + + test = doctest.testmod() + print(test)