def _check_daylong(tr):
if len(np.nonzero(tr.data)[<NUM_LIT:0>]) < <NUM_LIT:0.5> * len(tr.data):<EOL><INDENT>qual = False<EOL><DEDENT>else:<EOL><INDENT>qual = True<EOL><DEDENT>return qual<EOL>
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