phred.py 文件源码

def proba_to_quality_sanger(pe):
    """A value between 0 and 93

    :param pe: the probability of error.
    :return: Q is the quality score.

    - a high probability of error (0.99) gives Q=0
    - q low proba of errors (0.05) gives Q = 13
    - q low proba of errors (0.01) gives Q = 20

    """
    if pe > 1:
        pe = 1
    if pe < 1e-90:
        pe = 1e-90
    Qs = -10 * log10(pe)
    if Qs > 93:
        Qs = 93
    return Qs