implementation of from_julian_date()

[sebhahn]

pandas.DatetimeIndex supports a method called to_julian_date() would it be easily possible to support a function/method doing the opposite, i.e. from_julian_date()?

[chris-b1]

fyi, this is somewhat easy to do with the current to_datetime, just subtract the offset and specify that the unit is days.

In [66]: julian_dates = pd.date_range('2014-1-1', periods=10).to_julian_date().values

In [67]: julian_dates
Out[67]: 
array([ 2456658.5,  2456659.5,  2456660.5,  2456661.5,  2456662.5,
        2456663.5,  2456664.5,  2456665.5,  2456666.5,  2456667.5])

In [68]: pd.to_datetime(julian_dates - pd.Timestamp(0).to_julian_date(), unit='D')
Out[68]: 
DatetimeIndex(['2014-01-01', '2014-01-02', '2014-01-03', '2014-01-04',
               '2014-01-05', '2014-01-06', '2014-01-07', '2014-01-08',
               '2014-01-09', '2014-01-10'],
              dtype='datetime64[ns]', freq=None)

[sebhahn]

interesting solution, thank you very much for that!

[jreback]

I think this would not be unreasonable to have pd.to_datetime(....., ,unit='julian')
I guess as long as making things up DatetimeIndex.astype('datetime64[julian]') prob a bit much

We don't have any from_* for this kind of thing

[sebhahn]

Good idea! So you plan to support this in the future?

[jreback]

@sebhahn if you'd like to do a PR with the unit='julian' I think would be reasonable to start.

[sumitbinnani]

@jreback @sebhahn
Is this enhancement being included, and is someone working on the same? If not, I would like to give it a try :-)

[sebhahn]

@sumitbinnani I haven't started yet, so feel free to implement it 😄

[sumitbinnani]

@sebhahn: Thanks. Will soon submit a patch :-)