transform.py 文件源码

def _transform_y(y, lam):
    """Transform a single y, given a single lambda value.
    No validation performed.

    Parameters
    ----------

    y : array_like, shape (n_samples,)
       The vector being transformed

    lam : ndarray, shape (n_lambdas,)
       The lambda value used for the transformation
    """
    # ensure np array
    y = np.array(y)
    y_prime = np.array([(np.power(x, lam) - 1) / lam if not _eqls(lam, ZERO) else log(x) for x in y])

    # rarely -- very rarely -- we can get a NaN. Why?
    return y_prime