to_pandas() from binned timed series with bin_time_start

Description

I had a problem with astropy binned time series. I have created such an object using the aggregate_downsample function where I specify the time_bin_start = TimeDelta(-600.,format=‘sec’). When I try to use the to_pandas() function on this binned time series, I get the following error:

  File "C:\Users\bmm93\anaconda3\lib\site-packages\astropy\table\table.py", line 3314, in to_pandas
    kwargs = {'index': out.pop(index)} if index else {}
KeyError: 'time_bin_start'

I have not had trouble with to_pandas() before specifying time_bin_start.

I got response from a user on the ‘Python users in Astronomy’ Facebook group: “This looks like astropy 4.0.x, and a real bug at that. Unfortunately with 4.3 or later I can confirm the same even without specifying time_bin_start! It should work with to_pandas(index=False) – can you check if that returns sensible results? But it would be great if you could submit an issue about this.”

I then tried ‘to_pandas(index=False)’ and I got sensible results. I am using astropy version 4.0.2.

Expected behavior

Actual behavior

Steps to Reproduce

1. [First Step]
2. [Second Step]
3. [and so on…]

# Put your Python code snippet here.

System Details

[dhomeier]

Thanks for the bug report! To point out the respective behaviour in 4.0, 4.3 and 5.0, current dev gives

>>> tss = timeseries.aggregate_downsample(ts, time_bin_size=5*u.s)
>>> tss.to_pandas()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/derek/opt/lib/python3.9/site-packages/astropy/table/table.py", line 3744, in to_pandas
    idx = out.pop(index)
KeyError: 'time_bin_start'

even without a time_bin_start option given, whereas the older versions have

>>> tss = timeseries.aggregate_downsample(ts, time_bin_size=5*u.s, time_bin_start=input_time[1])
>>> tss.to_pandas()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/lib/python3.6/site-packages/astropy/table/table.py", line 3310, in to_pandas
    kwargs = {'index': out.pop(index)} if index else {}
KeyError: 'time_bin_start'

– in 4.0.2-4.0.5 only with the time_bin_start option, in 4.3 even without. In all versions both workarounds pass, though with different results/formats:

>>> tss.to_pandas(index=False)
   time_bin_start.jd1  time_bin_start.jd2  time_bin_size           a
0           2457470.0            0.021169            5.0    5.333333
1           2457470.0            0.021227            5.0   30.333333
2           2457470.0            0.021285            5.0  135.666667
>>> table.Table(tss).to_pandas()
                     time_bin_size           a
time_bin_start                                
2016-03-22 12:30:29            5.0    5.333333
2016-03-22 12:30:34            5.0   30.333333
2016-03-22 12:30:39            5.0  135.666667

[taldcroft]

I think I have a fix, PR coming hopefully.