def test_groupby_reduce(self):
data = Dataset({'xy': (['x', 'y'], np.random.randn(3, 4)),
'xonly': ('x', np.random.randn(3)),
'yonly': ('y', np.random.randn(4)),
'letters': ('y', ['a', 'a', 'b', 'b'])})
expected = data.mean('y')
actual = data.groupby('x').mean()
self.assertDatasetAllClose(expected, actual)
actual = data.groupby('x').mean('y')
self.assertDatasetAllClose(expected, actual)
expected = Dataset({'xy': data['xy'].groupby('letters').mean(),
'xonly': data['xonly'].mean(),
'yonly': data['yonly'].groupby('letters').mean()})
actual = data.groupby('letters').mean()
self.assertDatasetAllClose(expected, actual)
