
        
        
            
                
                
                    df = spark.createDataFrame([["Alex", 25], ["Bob", 30]], ["name", "age"])
df.show()
                
            
            +----+---+
|name|age|
+----+---+
|Alex| 25|
| Bob| 30|
+----+---+

Getting the mean of a PySpark column

To obtain the mean age:


        
        
            
                
                
                    import pyspark.sql.functions as F
df.select(F.mean("age")).show()
                
            
            +--------+
|avg(age)|
+--------+
|    27.5|
+--------+

To get the mean age as an integer:


        
        
            
                
                
                    list_rows = df.select(F.mean("age")).collect()
list_rows[0][0]
                
            
            27.5

Here, we are converting the PySpark DataFrame returned from select(~) into a list of Row objects using the collect() method. This list is guaranteed to be of size one because the mean(~) reduces column values into a single number. To access the content of the Row object, we use another [0].

Getting the mean of each group in PySpark

Consider the following PySpark DataFrame:


        
        
            
                
                
                    df = spark.createDataFrame([["Alex", 20, "A"],\
                            ["Bob", 30, "B"],\
                            ["Cathy", 50, "A"]],
                            ["name", "age", "class"])
df.show()
                
            
            +-----+---+-----+
| name|age|class|
+-----+---+-----+
| Alex| 20|    A|
|  Bob| 30|    B|
|Cathy| 50|    A|
+-----+---+-----+

To get the mean age of each class:


        
        
            
                
                
                    df.groupby("class").agg(F.mean("age").alias("MEAN AGE")).show()
                
            
            +-----+--------+
|class|MEAN AGE|
+-----+--------+
|    A|    35.0|
|    B|    30.0|
+-----+--------+

Here, we are using alias("MEAN AGE") to assign a label to the aggregated age column.

Published by Isshin Inada

Edited by 0 others

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Official PySpark Documentation

https://spark.apache.org/docs/latest/api/python/reference/api/pyspark.sql.functions.mean.html

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