API: remove datetime-like index ops from Series

[jreback]

as per discussed in #7146. may provide a to_index() and/or an accessor in future versions

[jreback]

@cpcloud @jorisvandenbossche ?

[jorisvandenbossche]

This is a bit cryptic I think. On the one hand you say that Series and Index share common operators, but then you say weekday is removed and datetimeindex methods on a series will raise (so this is not sharing).

Are the changes that are relevant to users not:

• Series.weekday is removed (and actually should first be deprecated?)
• min/max/unique/nunique/value_counts methods are added to Index types (that they are shared with Series is an implementation detail, no?)

[jorisvandenbossche]

Just added a note about the new whatsnew entry, but for the rest am OK on disabling this for now.

[jreback]

@jorisvandenbossche fair comments

the issue is that it can become ambiguous, so don't want to add something w/o dealing with that.

Series.weekday wasn't documented at all so I don't think a big deal to remove.

[jorisvandenbossche]

@jreback OK for the weekday

What do you mean with ambiguous? What can become ambiguous? min/max/unique/nunique/value_counts will not always act on the series values?

[jreback]

not the usage of Series.weekday could be ambiguous (and applies to all of the properties), IF the series contains a datetimeindex as well (or periodindex)

In [1]: s      = Series(pd.date_range('20130101',periods=3),index=pd.date_range('20130104',periods=3))

In [2]: s
Out[2]: 
2013-01-04   2013-01-01
2013-01-05   2013-01-02
2013-01-06   2013-01-03
Freq: D, dtype: datetime64[ns]

In [3]: s.index.weekday
Out[3]: array([4, 5, 6])

In [4]: pd.DatetimeIndex(s).weekday
Out[4]: array([1, 2, 3])

[jorisvandenbossche]

ah yes OK, weekday is indeed ambiguous like the other datetime accessors. And so they are disabled again in this PR. That's all OK (but I thought you were speaking about the others)

[jreback]

no, the others were added (not in this PR necessarily, though max/min were), but don't think had any notes on them

[jorisvandenbossche]

What was actually added? (I just realize I don't fully understand this)

For example max() already is an index method in 0.13, so I don't fully get what support 'max()/... on Index types' in the release notes is supposed to mean?

[jreback]

all of these were added as mixin methods that is they were moved from index/series directly to the ops mixin class (so max.min) were not added to index

but the other were added to index

[jorisvandenbossche]

There still some occurences in the docs (that now error):

http://pandas-docs.github.io/pandas-docs-travis/timeseries.html#custom-business-days-experimental
http://pandas-docs.github.io/pandas-docs-travis/whatsnew.html#experimental-features