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# scipy.linalg.tril

`scipy.linalg.``tril`(m, k=0)

  Make a copy of a matrix with elements above the k-th diagonal zeroed.

  Parameters: | m : array_like Matrix whose elements to return k : int, optional Diagonal above which to zero elements. k == 0 is the main diagonal, k < 0 subdiagonal and k > 0 superdiagonal.
  Returns: | tril : ndarray Return is the same shape and type as m.

  Examples

      >>> from scipy.linalg import tril
      >>> tril([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
      array([[ 0,  0,  0],
             [ 4,  0,  0],
             [ 7,  8,  0],
             [10, 11, 12]])