def _mask_non_positives(a):
mask = a <= <NUM_LIT:0.0><EOL>if mask.any():<EOL><INDENT>return ma.MaskedArray(a, mask=mask)<EOL><DEDENT>return a<EOL>
Return a Numpy masked array where all non-positive values are
masked.  If there are no non-positive values, the original array
is returned.