Implement Akima1DInterpolator

[gliptak]

• closes Add Akima Interpolation to Pandas #7588
• tests added / passed
• passes git diff upstream/master | flake8 --diff
• whatsnew entry

[gliptak]

This build failed https://travis-ci.org/pydata/pandas/jobs/121843938 likely because of the Scipy version.

axis was added to Akima1DInterpolator at 0.17.0 as per scipy/scipy@b0395b4

Is there a minimum version of Scipy for pandas? What would be a good way to handle lower versions?

Thanks

[jreback]

pls have an expected case and use assert_series_equal

[gliptak]

Added assert

[jreback]

you can you call this in a try: except to handle the scipy signature differences. (then if it doesn't work in the excpet, raise again). we don't have a min version.

[jreback]

so need a test for this. on the 2.7_LOCALE build we install a really old scipy. We may need to install a somewhat newer one on another build to explicity test for this. When did this Akima1DInterpolate appear in scipy? and seems the axis parm was added in 0.17.0?

[gliptak]

0.14.0 (as per scipy/scipy@a0a3b38) I implemented a different check.

[jreback]

ok the 3.4 build has scipy==0.14.0 installed so pls verify that the test works corretctly (IOW it is NOT skipped, but passes).

remove scipy from ci/requirements-3.5_OSX. Make sure that you DO see some skips. I don't think we were testing having NO scipy.

[jreback]

ok , just remove scipy from ci/requirements-3.5_OSX and I think will be good to go.

[gliptak]

from ci/requirements-3.5_OSX.run ?

[jreback]

yep (we are including a version of scipy on EVERY build, so need to take it from one)

[gliptak]

Done

[gliptak]

The two test failures seem to be unrelated.

[gliptak]

The two test failures seem to be unrelated.

[jreback]

can you change this (and the pchip one to something like):

if method == 'akima':
    alt_methods['akima'] = _akima_interpolate

Move to _akima_interpolate

    from scipy.interpolate import Akima1DInterpolator  # noqa

[gliptak]

Updated.

[jreback]

pls add a whatsnew as well

[gliptak]

Added whatsnew

[jreback]

yes this is fine

[jreback]

pls squash

[jreback]

add a small note when to use this in : http://pandas-docs.github.io/pandas-docs-travis/missing_data.html#interpolation (you might want to break up that section a bit and make it into a table)

[jreback]

add to the doc-string for .interpolate with a versionadded tag

[gliptak]

Added notes and versionadded tag

[jreback]

no this needs to be updated in pandas.core.generic.NDFrame.interpolate

[gliptak]

Moved section.

[gliptak]

Updated per comments.

[jreback]

good

[jreback]

ok, looks good. ping when green (and pls verify that tests are skipped as appropriate)

[jorisvandenbossche]

You need two spaces here at the beginning of this line, so the start of the text is aligned with the start of the text in the previous line ('If ...')

[gliptak]

Done

[jorisvandenbossche]

The 'support for 'akima'' should go on the next line I think. See the sphinx docs: http://www.sphinx-doc.org/en/stable/markup/para.html#directive-versionadded for an example. And then maybe change the text to something like "Added support for the 'akima' method"

[gliptak]

Changed.

[jorisvandenbossche]

@gliptak I just added some more doc comments, looks very good for the rest!

[gliptak]

@jreback Build is green. Tests skipped https://s3.amazonaws.com/archive.travis-ci.org/jobs/122101334/log.txt

#268 pandas.tests.test_generic.TestSeries.test_interpolate_akima: no scipy.stats module
#269 pandas.tests.test_generic.TestSeries.test_interpolate_corners: no scipy.stats module
#270 pandas.tests.test_generic.TestSeries.test_interpolate_pchip: no scipy.stats module

I also opened #12856 (consistently fails the same way)

[jreback]

@gliptak thanks!

pls review the built docs for accuracy (and good looking ness) and issue a follow up if necessary. (prob will take a few hours before they are built)

[gliptak]

@jreback @jorisvandenbossche Thank you for guiding this through

[gliptak]

Docs updated good.