def Cov(xs, ys, meanx=None, meany=None):
 xs = np.asarray(xs)
 ys = np.asarray(ys)
 if (meanx is None):
  meanx = np.mean(xs)
 if (meany is None):
  meany = np.mean(ys)
 cov = (np.dot((xs - meanx), (ys - meany)) / len(xs))
 return cov

def Cov ( xs , ys , meanx = None , meany = None ) : xs = np . asarray ( xs ) ys = np . asarray ( ys ) if ( meanx is None ) : meanx = np . mean ( xs ) if ( meany is None ) : meany = np . mean ( ys ) cov = ( np . dot ( ( xs - meanx ) , ( ys - meany ) ) / len ( xs ) ) return cov
computes cov .