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Pandas Series agg() Method

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Pandas is one of those packages and makes importing and analyzing data much easier. Pandas Series.agg() is used to pass a function or list of functions to be applied on a series or even each element of the series separately. In the case of a list of functions, multiple results are returned by the Series.agg() method.

Pandas Series Aggregate Syntax

Syntax: Series.agg(func, axis=0) 

Parameters: 

  • func: Function, list of function or string of function name to be called on Series. 
  • axis:0 or ‘index’ for row wise operation and 1 or ‘columns’ for column wise operation. 

Return Type: The return type depends on return type of function passed as parameter.

Aggregate the Series Elements in Pandas

In Pandas, series elements can be aggregated by computing statistical measures such as sum, mean, min, max, and count. These functions can provide insights into the dataset’s characteristics.

Python3




import pandas as pd
s = pd.Series([89,99,78,70])
s.agg('min')
s.agg(['min', 'max'])


Output:

min    70
max   99

Example 1: In this example, a Python lambda function is passed which simply adds 2 to each value of the series. Since the function will be applied to each value of the series, the return type is also a series. A random series of 10 elements is generated by passing an array generated using Numpy random method.

Python3




# importing pandas module
import pandas as pd
 
# importing numpy module
import numpy as np
 
# creating random arr of 10 elements
arr = np.random.randn(10)
 
# creating series from array
series = pd.Series(arr)
 
# calling .agg() method
result = series.agg(lambda num: num + 2)
 
# display
print('Array before operation: \n', series,
      '\n\nArray after operation: \n', result)


Output: 

As shown in the output, the function was applied to each value and 2 was added to each value of the series.

Array before operation: 
 0   -0.178400
1   -0.014408
2   -2.185778
3    0.335517
4    1.013446
5    0.897206
6    0.116324
7   -1.046006
8   -0.918818
9    0.552542
dtype: float64 
Array after operation: 
 0    1.821600
1    1.985592
2   -0.185778
3    2.335517
4    3.013446
5    2.897206
6    2.116324
7    0.953994
8    1.081182
9    2.552542
dtype: float64

Example 2: Passing List of functions In this example, a list of some of Python’s default functions is passed and multiple results are returned by Pandas Series.agg() method into multiple variables. 

Python3




# importing pandas module
import pandas as pd
 
# importing numpy module
import numpy as np
 
# creating random arr of 10 elements
arr = np.random.randn(10)
 
# creating series from array
series = pd.Series(arr)
 
# creating list of function names
func_list = [min, max, sorted]
 
# calling .agg() method
# passing list of functions
result1, result2, result3 = series.agg(func_list)
 
# display
print('Series before operation: \n', series)
print('\nMin = {}\n\nMax = {},\
      \n\nSorted Series:\n{}'.format(result1, result2, result3))


Output: 

As shown in the output, multiple results were returned. Min, Max, and Sorted array were returned into different variables result1, result2, and result3 respectively.

Series before operation: 
 0   -1.493851
1   -0.658618
2    0.265253
3   -0.503875
4    1.419182
5    0.221025
6   -0.712019
7   -1.462868
8   -0.341504
9   -0.338337
dtype: float64
Min = -1.4938513079840412
Max = 1.4191824761086351,      
Sorted Series:
[-1.4938513079840412, -1.462868259420631, -0.7120191767162937, -0.6586184541010776, 
-0.5038754446324809, -0.34150351227216663, -0.33833663286234356,
 0.22102480822109685, 0.2652526809574672, 1.4191824761086351]


Last Updated : 23 Aug, 2023
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