Datetime / calendar histograms

[janpipek]

Requirements:

Possible axes: 1) month (cyclic) 2) year (continuous) 3) year+month (continuous) 4) day (continuous) 5) hour (cyclic) 6) weekday (cyclic) 7) week+weekday (continuous) 8) year + week (continuous) ...

Properties: 1) It must be possible to have a float quantity on other axes

Use case:

I have the following data:

2010-03-10, 4.3 deg
2010-03-11, -0.3 deg
...
2017-03-13, 3.4 deg
2017-03-14, 6.2 deg

I need a simple way to construct the histogram temperature vs. month of the year, ideally just calling h2...

Compatibility:

• must work with date, datetime objects
• must work with pandas internal and nat values

[janpipek]

Further requirements:

• enable merging
• enable flattening (year,month -> year+month