Adding several columns at the same time with multiindex

Question

I have a dataframe with a variable number of columns and with are handled inside MultiIndex for the columns. I'm trying to add several columns into the same MultiIndex structure

I've tried to add the new columns like if I would if there was only one column but it doesn't work

I have tried this:

df = pd.DataFrame(np.random.rand(4,2), columns=pd.MultiIndex.from_tuples([('plus_zero', 'A'), ('plus_zero', 'B')]))

df['plus_one'] = df['plus_zero'] + 1

But I get ValueError: Wrong number of items passed 2, placement implies 1.

The original df should look like this:

  plus_zero          
          A         B
0  0.602891  0.701130
1  0.395749  0.960206
2  0.268238  0.140606
3  0.165802  0.971707

And the result I want:

  plus_zero            plus_one          
          A         B         A         B
0  0.602891  0.701130  1.602891  1.701130
1  0.395749  0.960206  1.395749  1.960206
2  0.268238  0.140606  1.268238  1.140606
3  0.165802  0.971707  1.165802  1.971707

federicober · Accepted Answer · 2019-04-23 09:52:45Z

2

Using pd.concat:

You must specify the names of the new columns and the axis=1 or axis='columns'

pd.concat([df.loc[:,'plus_zero'],df.loc[:,'plus_zero']+1],
          keys=['plus_zero','plus_one'],
          axis=1)

  plus_zero            plus_one          
          A         B         A         B
0  0.049735  0.013907  1.049735  1.013907
1  0.782054  0.449790  1.782054  1.449790
2  0.148571  0.172844  1.148571  1.172844
3  0.875560  0.393258  1.875560  1.393258

edited Apr 23, 2019 at 9:52

federicober

3831 gold badge2 silver badges11 bronze badges

answered Apr 19, 2019 at 16:02

BENY

324k22 gold badges176 silver badges250 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Adding several columns at the same time with multiindex

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related