ENH: Scatter plot now supports errorbar

[sinhrks]

This is enhancement for #5638. I sometimes want to plot scatter with errorbars, thus I've refactored to support it.

Also, this includes following fixes. I've also modified tests to check the number of errorbars actually drawn.

• There are some types which expected to work, but results in ValueError.
  • float (MPL can accept it)
  • unicode (in Python 2.x)
  • Other list-like, such as iterator
• A bug related to time series.

>>> s = Series(rand(6), index=range(6), name='x')
>>> err_df = DataFrame(rand(6, 3) / 10, index=range(6), columns=['x', 'y', 'z'])
>>> s.plot(yerr=err_df)               # This works, errorbar appears using err_df x column

>>> s.index = tm.makeDateIndex(k=6)
>>> s.plot(yerr=err_df)               # But this doesn't, errorbar doesn't appear

[jtratner]

can you rebase this on top of master again, then we can review

[sinhrks]

Sure. Rebased.

[jreback]

@TomAugspurger can you give a look see

[jreback]

@sinhrks need a release note for this pls

[sinhrks]

Rebased. I've thought release note is not requreid because error bar itself is new function of v0.14, and release note has following description. Should I prepare separate one?

Added error bar support to the .plot method of DataFrame and Series (:issue:3796)

[jreback]

oh just add this note number (or pr numbe) to that one

[sinhrks]

OK, added PR number.

[jreback]

@sinhrks @TomAugspurger

[TomAugspurger]

Thanks @sinhrks. Could you rebase off master now that the Area plot is merged? There are a few conflicts in tools/plotting.py Other than the we're good.

[sinhrks]

@TomAugspurger Sure, rebased to latest master. Plotting test has been passed in Travis, and looks fail in offset test.

[jreback]

pls rebase 1 more time, master is fixed up

[sinhrks]

Thanks, rebased.

[TomAugspurger]

Thanks.

@jreback a failure in pandas.io.tests.test_packers.TestNumpy and pandas.io.tests.test_packers.TestNumpy under the allowed failures build. Is this OK?

[jreback]

@TomAugspurger yeh...thouse fail every once in a while on 3.4, not really sure why. if you would like to investigate give it a go!

otherwise this PR is ok

[TomAugspurger]

Excellent. Thanks @sinhrks