Table of Contents
To calculate the average of selected columns in Pandas, one would use the mean() function to specify the columns to be included in the calculation. For example, to calculate the average of a dataframe’s “A” and “B” columns, one would write df[‘A’, ‘B’].mean(). This will return the average of the two specified columns.
You can use the following methods to calculate the average row values for selected columns in a pandas DataFrame:
Method 1: Calculate Average Row Value for All Columns
df.mean(axis=1)
Method 2: Calculate Average Row Value for Specific Columns
df[['col1', 'col3']].mean(axis=1)
The following examples shows how to use each method in practice with the following pandas DataFrame:
import pandas as pd #create DataFrame df = pd.DataFrame({'points': [14, 19, 9, 21, 25, 29, 20, 11], 'assists': [5, 7, 7, 9, 12, 9, 9, 4], 'rebounds': [11, 8, 10, 6, 6, 5, 9, 12]}) #view DataFrame df points assists rebounds 0 14 5 11 1 19 7 8 2 9 7 10 3 21 9 6 4 25 12 6 5 29 9 5 6 20 9 9 7 11 4 12
Method 1: Calculate Average Row Value for All Columns
The following code shows how to create a new column in the DataFrame that displays the average row value for all columns:
#define new column that shows the average row value for all columns
df['average_all'] = df.mean(axis=1)
#view updated DataFrame
df
points assists rebounds average_all
0 14 5 11 10.000000
1 19 7 8 11.333333
2 9 7 10 8.666667
3 21 9 6 12.000000
4 25 12 6 14.333333
5 29 9 5 14.333333
6 20 9 9 12.666667
7 11 4 12 9.000000
Here’s how to interpret the output:
The average value of the first row is calculated as: (14+5+11) / 3 = 10.
The average value of the second row is calculated as: (19+7+8) / 3 = 11.33.
And so on.
Method 2: Calculate Average Row Value for Specific Columns
The following code shows how to calculate the average row value for just the “points” and “rebounds” columns:
#define new column that shows average of row values for points and rebounds columns
df['avg_points_rebounds'] = df[['points', 'rebounds']].mean(axis=1)
#view updated DataFrame
df
points assists rebounds avg_points_rebounds
0 14 5 11 12.5
1 19 7 8 13.5
2 9 7 10 9.5
3 21 9 6 13.5
4 25 12 6 15.5
5 29 9 5 17.0
6 20 9 9 14.5
7 11 4 12 11.5
The average value of “points” and “rebounds” in the first row is calculated as: (14+11) / 2 = 12.5.
The average value of “points” and “rebounds” in the second row is calculated as: (19+8) / 2 = 13.5.
And so on.
The following tutorials explain how to perform other common operations in Python: