Find the column name which has the maximum value for each row

Question

I have a DataFrame like this one:

In [7]:
frame.head()
Out[7]:
Communications and Search   Business    General Lifestyle
0   0.745763    0.050847    0.118644         


        

Answer 1

You could apply on dataframe and get argmax() of each row via axis=1

In [144]: df.apply(lambda x: x.argmax(), axis=1)
Out[144]:
0    Communications
1          Business
2    Communications
3    Communications
4          Business
dtype: object

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Here's a benchmark to compare how slow apply method is to idxmax() for len(df) ~ 20K

In [146]: %timeit df.apply(lambda x: x.argmax(), axis=1)
1 loops, best of 3: 479 ms per loop

In [147]: %timeit df.idxmax(axis=1)
10 loops, best of 3: 47.3 ms per loop