Python: Scaling numbers column by column with pandas

Question

I have a Pandas data frame \'df\' in which I\'d like to perform some scalings column by column.

• In column \'a\', I need the maximum number to be 1, the minimum

Answer 1

You could subtract by the min, then divide by the max (beware 0/0). Note that after subtracting the min, the new max is the original max - min.

In [11]: df
Out[11]:
    a    b
A  14  103
B  90  107
C  90  110
D  96  114
E  91  114

In [12]: df -= df.min()  # equivalent to df = df - df.min()

In [13]: df /= df.max()  # equivalent to df = df / df.max()

In [14]: df
Out[14]:
          a         b
A  0.000000  0.000000
B  0.926829  0.363636
C  0.926829  0.636364
D  1.000000  1.000000
E  0.939024  1.000000

To switch the order of a column (from 1 to 0 rather than 0 to 1):

In [15]: df['b'] = 1 - df['b']

An alternative method is to negate the b columns first (df['b'] = -df['b']).