Dear all, The sentences bellow will always raise an Error or Exception just as follows, which is a little anomaly. Is this a bug? >>> u1=numpy.random.rand(100000) >>> u2=numpy.random.rand(100000) >>> scipy.stats.kendalltau(u1,u2) --------------------------------------------------------------------------- AttributeError Traceback (most recent call last) /home/zfyuan/phd/paper1/pyvine_lap/<ipython-input-28-98f367090ed1> in <module>() ----> 1 sp.stats.kendalltau(u1,u2) /usr/lib64/python2.7/site-packages/scipy/stats/stats.pyc in kendalltau(x, y, initial_lexsort) 2673 2674 tau = ((tot - (v + u - t)) - 2.0 * exchanges) / \ -> 2675 np.sqrt((tot - u) * (tot - v)) 2676 2677 # what follows reproduces the ending of Gary Strangman's original AttributeError: sqrt -- Jeffrey