If omitted, no exception is raised.
nan_ok : bool, optional
    If nan is always an accepted result.
vectorized : bool, optional
    Whether all functions passed in are vectorized.
ignore_inf_sign : bool, optional
    Whether to ignore signs of infinities.
    (Doesn't matter for complex-valued functions.)
distinguish_nan_and_inf : bool, optional
    If True, treat numbers which contain nans or infs as
    equal. Sets ignore_inf_sign to be True.

Nc