between_time在熊猫面板上不起作用

Question

The method between_time is defined in a pandas panel object, I would expect this method to be applied to all dataframes in the panel, but this is not working. So what is this method doing?

Example

rng = pd.date_range('1/1/2013',periods=100,freq='D')
data = np.random.randn(100, 4)
cols = ['A','B','C','D']
df1, df2, df3 = pd.DataFrame(data, rng, cols), pd.DataFrame(data, rng, cols), pd.DataFrame(data, rng, cols)
pf = pd.Panel({'df1':df1,'df2':df2,'df3':df3})
pf.between_time('08:00:00', '09:00:00')

The above code returns this error

Traceback (most recent call last): File "", line 1, in File "/usr/lib64/python2.7/site-packages/pandas-0.14.0-py2.7-linux-x86_64.egg/pandas/core/generic.py", line 2796, in between_time raise TypeError('Index must be DatetimeIndex') TypeError: Index must be DatetimeIndex

Answer 1

You don't actually have any times that would be selected, so I changed your example a bit (you were using D frequency)

In [17]: rng = pd.date_range('1/1/2013',periods=100,freq='H')

In [18]: data = np.random.randn(100, 4)

In [19]: df1, df2, df3 = pd.DataFrame(data, rng, cols), pd.DataFrame(data, rng, cols), pd.DataFrame(data, rng, cols)

In [20]: pf = pd.Panel({'df1':df1,'df2':df2,'df3':df3})

In [21]: pf
Out[21]: 
<class 'pandas.core.panel.Panel'>
Dimensions: 3 (items) x 100 (major_axis) x 4 (minor_axis)
Items axis: df1 to df3
Major_axis axis: 2013-01-01 00:00:00 to 2013-01-05 03:00:00
Minor_axis axis: A to D

The axis parameter is not implemented at the moment, so you can do this:

In [22]: indexer = pf.major_axis.indexer_between_time('08:00','09:00')

In [23]: pf.take(indexer,axis='major')
Out[23]: 
<class 'pandas.core.panel.Panel'>
Dimensions: 3 (items) x 8 (major_axis) x 4 (minor_axis)
Items axis: df1 to df3
Major_axis axis: 2013-01-01 08:00:00 to 2013-01-04 09:00:00
Minor_axis axis: A to D