Absolute and Relative frequency in Pandas

In statistics, the term "frequency" indicates the number of occurrences of a value in a given data sample. As a software meant for mathematical and scientific analysis, Pandas has many in-built methods to calculate frequency from a given sample.

Absolute Frequency It is same as just the frequency where the number of occurrences of a data element is calculated. In the below example, we simply count the number of times the name of a city is appearing in a given DataFrame and report it out as frequency.

Approach 1 − We use the pandas method named .value_counts.

Example

import pandas as pd
# Create Data Frame
data = ["Chandigarh","Hyderabad","Pune","Pune","Chandigarh","Pune"]
# use the method .value_counts()
df = pd.Series(data).value_counts()
print(df)

Output

Running the above code gives us the following result −

Pune          3
Chandigarh    2
Hyderabad     1
dtype: int64

Approach 2 − We use the pandas method named .crosstab

Example

import pandas as pd
data = ["Chandigarh","Hyderabad","Pune","Pune","Chandigarh","Pune"]
df = pd.DataFrame(data,columns=["City"])
tab_result = pd.crosstab(index=df["City"],columns=["count"])
print(tab_result)

Output

Running the above code gives us the following result −

col_0        count
City
Chandigarh   2
Hyderabad    1
Pune         3

RelativeFrequency − This is a fraction between a given frequency and the total number of observations in a data sample. So the value can be a floating point value which can also be expressed as a percentage. To find it out we first calculate the frequency as shown in the first approach and then divide it with total number of observations which is found out using the len() function.

Example

import pandas as pd
# Create Data Frame
data = ["Chandigarh","Hyderabad","Pune","Pune","Chandigarh","Pune"]
# use the method .value_counts()
df = pd.Series(data).value_counts()
print(df/len(data))

Output

Running the above code gives us the following result −

Pune 0.500000
Chandigarh 0.333333
Hyderabad 0.166667
dtype: float64