Python Pandas - Get the minimum value from Ordered CategoricalIndex

To get the minimum value from an Ordered CategoricalIndex, use the catIndex.min() method in Pandas. This method returns the first category in the ordered sequence, not the alphabetically smallest value.

Creating an Ordered CategoricalIndex

First, let's create a CategoricalIndex with ordered categories ?

import pandas as pd

# Create an ordered CategoricalIndex
catIndex = pd.CategoricalIndex(
    ["p", "q", "r", "s", "p", "q", "r", "s"], 
    ordered=True, 
    categories=["p", "q", "r", "s"]
)

print("Categorical Index...")
print(catIndex)

Categorical Index...
CategoricalIndex(['p', 'q', 'r', 's', 'p', 'q', 'r', 's'], categories=['p', 'q', 'r', 's'], ordered=True, dtype='category')

Getting the Minimum Value

Use the min() method to get the minimum value from the ordered categorical ?

import pandas as pd

catIndex = pd.CategoricalIndex(
    ["p", "q", "r", "s", "p", "q", "r", "s"], 
    ordered=True, 
    categories=["p", "q", "r", "s"]
)

print("Categories:", catIndex.categories)
print("Minimum value:", catIndex.min())

Categories: Index(['p', 'q', 'r', 's'], dtype='object')
Minimum value: p

How It Works

The min() method returns the first category in the ordered sequence, which is "p" in this case. The order is determined by the categories parameter, not alphabetical order.

Example with Different Category Order

Let's see what happens when we change the category order ?

import pandas as pd

# Different category order
catIndex = pd.CategoricalIndex(
    ["p", "q", "r", "s", "p", "q", "r", "s"], 
    ordered=True, 
    categories=["s", "r", "q", "p"]  # Different order
)

print("Categories:", catIndex.categories)
print("Minimum value:", catIndex.min())

Categories: Index(['s', 'r', 'q', 'p'], dtype='object')
Minimum value: s

Conclusion

The min() method on an ordered CategoricalIndex returns the first category in the defined order, not the alphabetically smallest value. This makes it useful for working with ordinal data like ratings or grades.