Utils.py 文件源码

def get_expected_subsample_variety(dictionary, subsample_size):
    """Compute the expected variety of a subsample of given size drawn from a
    given frequency dictionary.
    """
    sample_size = sum(dictionary.values())
    if subsample_size > sample_size:
        raise ValueError(u'Not enough elements in dictionary')
    num_subsamples = binom(sample_size, subsample_size, exact=True)
    expected_variety = len(dictionary)
    for freq in dictionary.values():
        expected_variety -= _prob_no_occurrence(
            sample_size, subsample_size, freq, num_subsamples
        )
    return expected_variety