From SO: http://stackoverflow.com/questions/24247255/idiomatic-multiindex-column-assignment-in-pandas/24247513#24247513 http://stackoverflow.com/questions/24258781/advanced-cross-section-with-multi-index-in-pandas
ix = pd.MultiIndex.from_tuples(list(enumerate(np.random.choice(['A', 'B'], 5))))
df = pd.DataFrame({'Val': np.random.randint(0, 30, 5)}, index=ix).unstack().fillna(0)
df
Val
A B
0 27 0
1 0 3
2 0 7
3 9 0
4 0 19
I think this could be make to work (its column creation)
df['Half'] = df['Val']/2
concat soln Automatic broadcasting (but need to not 'align')
In [59]: concat([df['Val'],df['Val']/2],axis=1,keys=['Val','Half'])
Out[59]:
Val Half
A B A B
0 0 10 0.0 5.0
1 0 10 0.0 5.0
2 0 13 0.0 6.5
3 27 0 13.5 0.0
4 2 0 1.0 0.0
In [42]: In
[107]: df = pd.DataFrame(np.arange(5*12).reshape(-1,12), columns=col)
In [108]: df
Out[108]:
first A B
second a b a b
third 1 2 3 1 2 3 1 2 3 1 2 3
0 0 1 2 3 4 5 6 7 8 9 10 11
1 12 13 14 15 16 17 18 19 20 21 22 23
2 24 25 26 27 28 29 30 31 32 33 34 35
3 36 37 38 39 40 41 42 43 44 45 46 47
4 48 49 50 51 52 53 54 55 56 57 58 59
In [109]: df.loc[:,idx[:,:,[2,3]]]-np.tile(df.loc[:,idx[:,:,1]].values,2)
Out[109]:
first A B
second a b a b
third 2 3 2 3 2 3 2 3
0 1 -1 -2 -4 7 5 4 2
1 1 -1 -2 -4 7 5 4 2
2 1 -1 -2 -4 7 5 4 2
3 1 -1 -2 -4 7 5 4 2
4 1 -1 -2 -4 7 5 4 2
Comment From: mroeschke
Looks like this raises a specific ValueError now so it looks intentional that this shouldn't be supported I suppose. Closing but happy to reopen if I misunderstood