nan in scikit_learn demo

[ucasiggcas]

hi,dear directly run the demo, but see the nan , what's the matter?

[------------] Total time cost: 0.42 (sec)
(array([[       nan, -1.63379  ],
       [       nan, -0.0229995],
       [       nan,  0.0296314],
       [       nan,  0.423044 ],
       [       nan,  0.249938 ]]), None)

thx