Creating a new column in a DataFrame based on multiple condition using values from another column in Python

Question

I would like to create a new column base on conditions from the Spread column.
The logic is:

if Spread is <= 4 then New_column = 4

if Spread is >4 and <=8 then New_column = 8

if Spread is >8 and <=12 Then new New_column = 12

if Spread is >12 Then new New_column = 16 (16 is the cut off.)

I have tried using .where but I have not any luck.
I would like the final output to look like below

Spread	New_Column
1	4
2	4
5	8
6	8
9	12
11	12
13	16

Asked By: Jay

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Source

Answer 1

Perhaps you can use pd.cut:

df['New_Column_2'] = (pd.cut(df['Spread'], [0, 4, 8, 12, np.inf]).cat.codes + 1) * 4
print(df)

Prints:

   Spread  New_Column  New_Column_2
0       1           4             4
1       2           4             4
2       5           8             8
3       6           8             8
4       9          12            12
5      11          12            12
6      13          16            16
7      24          16            16

Answered By: Andrej Kesely

Answer 2

You can use apply and create a function:

import pandas as pd
import numpy as np

df = pd.DataFrame({
    'Spread': [1,2,5,6,9,11,13]
})

def my_func(x): # Your function with your conditions
    if x <= 4:
        return 4
    elif x > 4 and x <= 8:
        return 8
    elif x > 8 and x <= 12:
        return 12
    elif x > 12:
        return 16
    else:
        return np.nan # In case none of your criteria is met

df['New_Column'] = df['Spread'].apply(my_func)

df is now:

   Spread  New_Column
0       1           4
1       2           4
2       5           8
3       6           8
4       9          12
5      11          12
6      13          16

Answered By: Marcelo Paco

Answer 3

The equal spacing of your conditions allows for:

df = pd.DataFrame({'Spread':[1,2,5,6,9,11,13,20]})
df['NewCol'] = df['Spread'].apply(lambda x: min( 4*(1+(x//4)), 16) )

Answered By: vogelito

Creating a new column in a DataFrame based on multiple condition using values from another column in Python

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