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How to convert Categorical features to Numerical Features in Python?

  • Last Updated : 26 Jan, 2022

It’s difficult to create machine learning models that can’t have features that have categorical values, such models cannot function. categorical variables have string-type values. thus we have to convert string values to numbers. This can be accomplished by creating new features based on the categories and setting values to them. In this article, we are going to see how to convert Categorical features to Numerical Features in Python

Stepwise Implementation

Step 1: Import the necessary packages and modules

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# import packages and modules
import numpy as np
import pandas as pd
from sklearn import preprocessing

Step 2: Import the CSV file

We will use the pandas read_csv() method to import the CSV file. To view and download the CSV file used click here.

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# import the CSV file
df = pd.read_csv('cluster_mpg.csv')
print(df.head())

Output:

Step 3: Get all features with categorical values

We use df.info() to find categorical features. Categorical features have Dtype as “object”.

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df.info()

Output:

In the given database columns “origin” and “name” is object type.

Step 4: Convert string values of origin column to numerical values

We will fit the “origin” column using preprocessing.LabelEncoder().fit() method.

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label_encoder = preprocessing.LabelEncoder()
label_encoder.fit(df["origin"])

Step 5: Get the unique values out of the categorical features

We will use label_encoder.classes_ attribute for this purpose.

classes_:ndarray of shape (n_classes,)

Holds the label for each class.

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# finding the unique classes
print(list(label_encoder.classes_))
print()

Output

['europe', 'japan', 'usa']

Step 6: Transforming the categorical values

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# values after transforming the categorical column.
print(label_encoder.transform(df["origin"]))

Output:


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