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scipy.linalg.

# rq

scipy.linalg.rq(a, overwrite_a=False, lwork=None, mode='full', check_finite=True)

  Compute RQ decomposition of a matrix.

  Calculate the decomposition `A = R Q` where Q is unitary/orthogonal and R upper triangular.

  Parameters:
    a(M, N) array_like

      Matrix to be decomposed

    overwrite_a bool, optional

      Whether data in a is overwritten (may improve performance)

    lwork int, optional

      Work array size, lwork >= a.shape[1]. If None or -1, an optimal size is computed.

    mode{‘full’, ‘r’, ‘economic’}, optional

      Determines what information is to be returned: either both Q and R (‘full’, default), only R (‘r’) or both Q and R but computed in economy-size (‘economic’, see Notes).

    check_finite bool, optional

      Whether to check that the input matrix contains only finite numbers. Disabling may give a performance gain, but may result in problems (crashes, non-termination) if the inputs do contain infinities or NaNs.

  Returns:
    R float or complex ndarray

      Of shape (M, N) or (M, K) for `mode='economic'`. `K = min(M, N)`.

    Q float or complex ndarray

      Of shape (N, N) or (K, N) for `mode='economic'`. Not returned if `mode='r'`.

  Raises:
    LinAlgError

      If decomposition fails.

  Notes

  This is an interface to the LAPACK routines sgerqf, dgerqf, cgerqf, zgerqf, sorgrq, dorgrq, cungrq and zungrq.

  If `mode=economic`, the shapes of Q and R are (K, N) and (M, K) instead of (N,N) and (M,N), with `K=min(M,N)`.

  Examples

      >>> import numpy as np
      >>> from scipy import linalg
      >>> rng = np.random.default_rng()
      >>> a = rng.standard_normal((6, 9))
      >>> r, q = linalg.rq(a)
      >>> np.allclose(a, r @ q)
      True
      >>> r.shape, q.shape
      ((6, 9), (9, 9))
      >>> r2 = linalg.rq(a, mode='r')
      >>> np.allclose(r, r2)
      True
      >>> r3, q3 = linalg.rq(a, mode='economic')
      >>> r3.shape, q3.shape
      ((6, 6), (6, 9))