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19 lines
497 B
Python
19 lines
497 B
Python
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import numpy as np
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def SST(A, b):
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# if the matrix is not upper triangular, we cannot solve the system
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if not np.allclose(A, np.triu(A)):
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print("The matrix A is not upper triangular!")
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return np.nan
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n = len(b)
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x = np.zeros((n, 1))
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# calculate xn
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x[n - 1, 0] = b[n - 1, 0] / A[n - 1, n - 1]
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# calculate x(i) backwards
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for i in range(n - 2, -1, -1):
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sum_of_xs = np.dot(A[i, (i + 1) : n], x[(i + 1) : n, 0])
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x[i, 0] = (b[i, 0] - sum_of_xs) / A[i, i]
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return x
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