BUG: Fix brittle pivot margins

[guyrt]

closes #3334 Brittle pivot margins

Issue was that pivot tables that use all columns of the original DataFrame in rows and cols failed on the margin computation. This is a special case for margins: one should use the index itself as the value.

>> df = DataFrame({'Response' : ['Y', 'N' ,'N', 'Y', 'Y', 'N'],
            'Type' : ['A', 'A', 'B', 'B', 'B', 'C']})

>> pivot_table(df, rows='Response',cols='Type',aggfunc=len,margins=True)
>> Type      A  B   C  All
>> Response               
>> N         1  1   1    3
>> Y         1  2 NaN    3
>> All       2  3   1    6

This is my first PR to Pandas, so apologies for anything out of the ordinary.

[jreback]

pls move the release notes to 0.13.thanks! (you prob need to rebase too)

[guyrt]

I moved release note to v0.13.0.txt and rebased the branch.

[jreback]

can you squash into 1-2 commits?

git rebase -i <commit 1 prior to yours>...then s/f

[jreback]

sorry..should have mentioned that before

[guyrt]

Fixed

[jreback]

pls add the issue here (and need in release notes as well)..thanks

[guyrt]

@jreback do you mean add the issue number, or an example that would fail without the change?

[jreback]

I meant (:issue:4358)....this creates a link in the document back to this actual issue

[jreback]

also...need to rebase on master (what happens is there are conflict on release notes....no biggie)....just rebase and i'll merge you right away

[guyrt]

woops! Turns out my origin master was out of date. Should have used upstream. Hang on, will fix.

[guyrt]

@jreback I made a new branch off master and cherry-picked my commits into it. I picked up a change in a test file
https://github.com/pydata/pandas/blob/master/pandas/tools/tests/test_pivot.py#L11
that makes my tests fail. Any idea what could have happened there?

[jreback]

you need to rebase this

something like

updates master to current

git checkout master
git pull

git branch my-branch --set-upstream master
git checkout my-branch
git pull --rebase

will bring you up to current

[guyrt]

Fixed - sorry.

[hayd]

@jreback for some reason I made the decision to never use pull (I like to use fetch/merge fast-forward/rebase so I don't get in sticky situations) but now I look again it looks like you can do that with pull too, cooool

git pull --ff-only

not sure I'll change.

[guyrt]

@jreback Travis is green. Any idea when this can get merged in?

[jreback]

@cpcloud can u take a look?

[jreback]

@guyrt thanks! merged in

[jreback]

via 69f5594