demo.py 文件源码

def cov_ellipse(cov, q=None, nsig=None, **kwargs):
    """ Code is slightly modified, but essentially borrowed from:
         https://stackoverflow.com/questions/18764814/make-contour-of-scatter
    """
    if q is not None:
        q = np.asarray(q)
    elif nsig is not None:
        q = 2 * norm.cdf(nsig) - 1
    else:
        raise ValueError('Either `q` or `nsig` should be specified')

    r2 = chi2.ppf(q, 2)
    val, vec = np.linalg.eigh(cov)
    width, height = 2 * np.sqrt(val[:, None] * r2)
    rotation = np.degrees(np.arctan2(*vec[::-1, 0]))

    return width, height, rotation