Created
February 5, 2014 16:41
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Functions to calculate the determinant of a matrix.
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def sign_factor(coords, matrix): | |
""" | |
Return the sign factor of the item in a matrix with | |
the coordinates specified by 'coords'. | |
""" | |
if (coords[0] % 2 == 0) != (coords[1] % 2 == 0): | |
return -1 | |
else: | |
return +1 | |
def minor(coords, matrix): | |
""" | |
Return the minor of the item in a matrix with | |
the coordinates specified by 'coords'. | |
""" | |
minor = [] | |
for i, row in enumerate(matrix): | |
if i != coords[0]: | |
minor_row = [] | |
for j, item in enumerate(row): | |
if j != coords[1]: | |
minor_row.append(item) | |
minor.append(minor_row) | |
return minor | |
def determinant(matrix): | |
""" | |
Return the determinant of a matrix. | |
""" | |
d = 0 | |
if len(matrix) == 1: | |
return matrix[0][0] | |
for i in range(len(matrix[0])): | |
d += matrix[0][i] * sign_factor((0, i), matrix) * determinant(minor((0, i), matrix)) | |
return d | |
A = [[1, 1, 2], | |
[3, 3, 5], | |
[6, 7, 7]] | |
print determinant(A) |
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