Regression with Linear Models

Regression is a type of supervised learning used to predict continuous numerical values.

Unlike classification, where we predict categories, regression estimates a numeric output based on input features.

The following are some example uses of regression:

• Predicting house prices based on square footage
• Estimating temperature from weather data
• Forecasting sales from historical trends

• Simple Linear Regression: Uses one feature to predict a target.
• Multiple Linear Regression: Uses multiple features to predict a target.
• Regularized Linear Regression: Adds a penalty to reduce overfitting (e.g., Ridge, Lasso).

The following example shows how to use linear regression to predict house prices.

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from sklearn.linear_model import LinearRegression
from sklearn.model_selection import train_test_split
from sklearn.metrics import mean_squared_error, r2_score
import numpy as np

# Sample dataset
X = np.array([[1000], [1500], [2000], [2500], [3000]])  # square footage
y = np.array([200000, 250000, 300000, 350000, 400000])  # prices

# Train/test split
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)

# Create and train model
model = LinearRegression()
model.fit(X_train, y_train)

# Predictions
y_pred = model.predict(X_test)

# Evaluation
mse = mean_squared_error(y_test, y_pred)
r2 = r2_score(y_test, y_pred)

print("Mean Squared Error:", mse)
print("R² Score:", r2)