Change defaults for resample

[changhiskhan]

maybe change closed and label both to 'left' to avoid confusion.

[wesm]

Urgh begrudgingly I agree this might be a good idea. Resampling to daily is a pretty big use case and the "right" way to do that is ts.resample('D', closed='left', label='left'). Maybe better to break code now vs. later. Ugh

[changhiskhan]

maybe the right solution is closed=None, label=None and set it to 'right' if resampling to 'M', 'A', 'Q', 'BM', 'BA', 'BQ', 'W' (where the dates are the ending dates) and 'left' for others?

[changhiskhan]

@wesm what do you think of the API change?
It's not too much magic to automatically infer the interval / label is it?

If we're happy with this I'll add some more tests.

[wesm]

I was thinking about it, and it seems D is really the only frequency that causes major confusion/problems, no?

[changhiskhan]

I think anything where the time stamp is the beginning of the period should have closed left and label left.
For example, resampling S to H, HH:59:59 should be the right bin edge.

[wesm]

Yeah, that's a fair point. Guess I should start a page on the website with "what's changed/broken in pandas since Python for Data Analysis was published" =|

[changhiskhan]

Or maybe even take all the book example code and maintain it as part of the pandas website?