/usr/lib64/python2.7/site-packages/numpy/ma/core.py:3791: UserWarning: Warning: converting a masked element to nan.
  warnings.warn("Warning: converting a masked element to nan.")
/usr/lib64/python2.7/site-packages/numpy/ma/core.py:3791: UserWarning: Warning: converting a masked element to nan.
  warnings.warn("Warning: converting a masked element to nan.")