How to Calculate the Mean of a Column in PySpark


You can use the following methods to calculate the mean of a column in a PySpark DataFrame:

Method 1: Calculate Mean for One Specific Column

from pyspark.sql import functions as F

#calculate mean of column named 'game1'
df.agg(F.mean('game1')).collect()[0][0]

Method 2: Calculate Mean for Multiple Columns

from pyspark.sql.functions import mean

#calculate mean for game1, game2 and game3 columns
df.select(mean(df.game1), mean(df.game2), mean(df.game3)).show()

The following examples show how to use each method in practice with the following PySpark DataFrame:

from pyspark.sql import SparkSession
spark = SparkSession.builder.getOrCreate()

#define data
data = [['Mavs', 25, 11, 10], 
        ['Nets', 22, 8, 14], 
        ['Hawks', 14, 22, 10], 
        ['Kings', 30, 22, 35], 
        ['Bulls', 15, 14, 12], 
        ['Blazers', 10, 14, 18]] 
  
#define column names
columns = ['team', 'game1', 'game2', 'game3'] 
  
#create dataframe using data and column names
df = spark.createDataFrame(data, columns) 
  
#view dataframe
df.show()

+-------+-----+-----+-----+
|   team|game1|game2|game3|
+-------+-----+-----+-----+
|   Mavs|   25|   11|   10|
|   Nets|   22|    8|   14|
|  Hawks|   14|   22|   10|
|  Kings|   30|   22|   35|
|  Bulls|   15|   14|   12|
|Blazers|   10|   14|   18|
+-------+-----+-----+-----+

Example 1: Calculate Mean for One Specific Column

We can use the following syntax to calculate the mean of values in the game1 column of the DataFrame only:

from pyspark.sql import functions as F

#calculate mean of column named 'game1'
df.agg(F.mean('game1')).collect()[0][0]

19.333333333333332

The mean of values in the game1 column turns out to be 19.333.

We can verify this is correct by manually calculating the mean of values in this column:

Mean of values in game1: (25 + 22 + 14 + 30 + 15 + 10) / 6 = 19.333.

Example 2: Calculate Mean for Multiple Columns

We can use the following syntax to calculate the mean of values for the game1, game2 and game3 columns of the DataFrame:

from pyspark.sql.functions import mean

#calculate mean for game1, game2 and game3 columns
df.select(mean(df.game1), mean(df.game2), mean(df.game3)).show()

+------------------+------------------+----------+
|        avg(game1)|        avg(game2)|avg(game3)|
+------------------+------------------+----------+
|19.333333333333332|15.166666666666666|      16.5|
+------------------+------------------+----------+

From the output we can see:

  • The mean of values in the game1 column is 19.333.
  • The mean of values in the game2 column is 15.167.
  • The mean of values in the game3 column is 16.5.

Note: If there are null values in the column, the mean function will ignore these values by default.

Additional Resources

The following tutorials explain how to perform other common tasks in PySpark:

How to Sum Multiple Columns in PySpark DataFrame
How to Add Multiple Columns to PySpark DataFrame
How to Add New Rows to PySpark DataFrame

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