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fish830617/null.py

Created January 5, 2016 16:01
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Calculate the null space of a matrix by QR factorization.
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null.py
# null.py
import numpy as np
from scipy.linalg import qr
def qr_null(A, tol=None):
Q, R, P = qr(A.T, mode='full', pivoting=True)
tol = np.max(A) * np.finfo(R.dtype).eps if tol is None else tol
rnk = min(A.shape) - np.abs(np.diag(R))[::-1].searchsorted(tol)
return Q[:, rnk:].conj()
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