code: def _check_daylong(tr):
      
      if len(np.nonzero(tr.data)[0]) < 0.5 * len(tr.data):
          qual = False
      else:
          qual = True
      return qual
docs: Check the data quality of the daylong file.
  
      Check to see that the day isn't just zeros, with large steps, if it is
      then the resampling will hate it.
  
      :type tr: obspy.core.trace.Trace
      :param tr: Trace to check if the data are daylong.
  
      :return quality (simply good or bad)
      :rtype: bool
  
      .. rubric:: Example
  
      >>> from obspy import read
      >>> from eqcorrscan.utils.pre_processing import _check_daylong
      >>> # Get the path to the test data
      >>> import eqcorrscan
      >>> import os
      >>> TEST_PATH = os.path.dirname(eqcorrscan.__file__) + '/tests/test_data'
      >>> st = read(TEST_PATH + '/WAV/TEST_/' +
      ...           '2013-09-01-0410-35.DFDPC_024_00')
      >>> _check_daylong(st[0])
      True