Calculate the frequency counts of each unique value of a Pandas series

Last Updated : 15 Sep, 2022

Let us see how to find the frequency counts of each unique value of a Pandas series. We will use these methods to calculate the frequency counts of each unique value of a Pandas series.

Using values_counts() to calculate the frequency of unique value

Here values_counts() function is used to find the frequency of unique value in a Pandas series.

Example 1 : Here we are creating a series and then with the help of values_counts() function we are calculating the frequency of unique values.

Python3

# importing the module
import pandas as pd

# creating the series
s = pd.Series(data = [2, 3, 4, 5, 5, 6, 
                      7, 8, 9, 5, 3])

# displaying the series
print(s)

# finding the unique count
print(s.value_counts())

Output :

Calculate the frequency counts of each unique value

Example 2 : Here we are randomly generating integer values and then finally calculating the counts for each value.

Python3

# importing the module
import pandas as pd

# creating the series
s = pd.Series(np.take(list('0123456789'), 
              np.random.randint(10, size = 40)))

# finding the unique count
s.value_counts()

# displaying the series
print(s)

Output :

Example 3 : Here we have a series where each value is a string and we are counting the occurrence of each element in the series.

Python3

# importing pandas as pd 
import pandas as pd 
  
# creating the Series 
sr = pd.Series(['Mumbai', 'Pune', 'Agra', 'Pune', 
                'Goa', 'Shimla', 'Goa', 'Pune']) 

# finding the unique count
sr.value_counts()

# displaying the series 

print(sr)

Output :

Using groupby() to calculate the frequency of unique value

Here we are using the groupby() function to group all the same values and then calculate their frequencies.

Python3

import pandas as pd

technologies = {
    "data":[2, 3, 4, 5, 5, 6, 
            7, 8, 9, 5, 3]
               }
df = pd.DataFrame(technologies)

df['frequency'] = df.groupby('data')
                  ['data'].transform('count')
print(df)

Output:

Using apply().fillna() function to calculate the frequency of unique value

Here we are filling NAN or 0 for the None values in the series and apply function to apply the same, and then calculate their frequencies.

Python3

import pandas as pd

technologies = {
    "data":[2, 3, 4, 5, 5, 6, 
            7, 8, 9, 5, 3]
               }
df = pd.DataFrame(technologies)

df1 = df.apply(pd.value_counts).fillna(0)

print(df1)