import matplotlib.pyplot as pl
import bluebell.plot as bbplot

A = np.random.rand(2,2)
C = A.T.dot(A)
mu = np.random.rand(2)
std = np.sqrt(np.diag(C))

bbplot.cov_ellipse(mu, C, ec='C0', fc='none')
pl.axis((mu + np.array([[-1.1],[1.1]])*std).T.flatten())