Machine Learning 3
๐งช Section 7: Model Evaluation & Hyperparameter Tuning
After building your machine learning model, it's crucial to evaluate its performance and fine-tune it to ensure it's neither underfitting nor overfitting.
In this section, we’ll explore:
-
Evaluation metrics for classification and regression
-
Overfitting vs. underfitting
-
Cross-validation techniques
-
Hyperparameter tuning with Grid Search and Random Search
✅ 7.1 Why Evaluate a Model?
Your model's accuracy on training data isn't enough. It must generalize well to unseen data. Evaluation helps answer:
-
How good is the model’s performance?
-
Is it biased or overfitted?
-
Which model is better when comparing several?
๐ฏ 7.2 Key Metrics for Classification
If your model predicts categories (e.g., spam or not spam), use these metrics:
Metric | Formula / Meaning |
---|---|
Accuracy | (TP + TN) / (Total) - Overall correct predictions |
Precision | TP / (TP + FP) - Correct positive predictions |
Recall | TP / (TP + FN) - Coverage of actual positives |
F1-score | Harmonic mean of Precision and Recall |
ROC-AUC | Trade-off between true positive and false positive |
from sklearn.metrics import classification_report, roc_auc_score
print(classification_report(y_test, y_pred))
print("ROC-AUC:", roc_auc_score(y_test, model.predict_proba(X_test)[:, 1]))
๐ 7.3 Confusion Matrix
The confusion matrix helps understand types of errors:
from sklearn.metrics import confusion_matrix
import seaborn as sns
import matplotlib.pyplot as plt
cm = confusion_matrix(y_test, y_pred)
sns.heatmap(cm, annot=True, fmt='d')
plt.xlabel('Predicted')
plt.ylabel('Actual')
plt.title('Confusion Matrix')
plt.show()
๐ 7.4 Evaluation Metrics for Regression
If your model predicts numeric values (e.g., house prices):
Metric | Use Case |
---|---|
MAE | Mean Absolute Error |
MSE / RMSE | Mean / Root Mean Squared Error |
R² Score | Variance explained by model |
from sklearn.metrics import mean_absolute_error, mean_squared_error, r2_score
mae = mean_absolute_error(y_test, y_pred)
rmse = mean_squared_error(y_test, y_pred, squared=False)
r2 = r2_score(y_test, y_pred)
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๐ 7.5 Cross-Validation
Train-test splits may vary with random seed. Cross-validation gives a better estimate of model performance.
๐ K-Fold Cross Validation
from sklearn.model_selection import cross_val_score
scores = cross_val_score(model, X, y, cv=5)
print("CV Accuracy:", scores.mean())
You can also use StratifiedKFold
for classification tasks with imbalanced data.
๐ 7.6 Underfitting vs. Overfitting
Term | Description | Fix |
---|---|---|
Underfitting | Model too simple, performs poorly on all data | Add complexity, features, or train longer |
Overfitting | Model too complex, great on training but bad on new data | Reduce complexity, use regularization, more data |
You can visualize learning curves to detect them.
๐ Learning Curve Plot
from sklearn.model_selection import learning_curve
train_sizes, train_scores, test_scores = learning_curve(
model, X, y, cv=5, scoring='accuracy', n_jobs=-1,
train_sizes=np.linspace(0.1, 1.0, 10)
)
train_mean = train_scores.mean(axis=1)
test_mean = test_scores.mean(axis=1)
plt.plot(train_sizes, train_mean, label="Training Score")
plt.plot(train_sizes, test_mean, label="Cross-Validation Score")
plt.xlabel("Training Set Size")
plt.ylabel("Accuracy")
plt.legend()
plt.title("Learning Curve")
plt.show()
๐งช 7.7 Hyperparameter Tuning
Hyperparameters are external configurations (e.g., n_estimators
, max_depth
) that must be manually tuned.
๐️ Grid Search
Tries all combinations of given parameters.
from sklearn.model_selection import GridSearchCV
param_grid = {
'n_estimators': [50, 100, 150],
'max_depth': [3, 5, 7],
'min_samples_split': [2, 4]
}
grid = GridSearchCV(RandomForestClassifier(), param_grid, cv=5)
grid.fit(X_train, y_train)
print("Best Parameters:", grid.best_params_)
print("Best Score:", grid.best_score_)
๐ฒ Random Search
Tries random combinations, useful when grid is too large.
from sklearn.model_selection import RandomizedSearchCV
from scipy.stats import randint
param_dist = {
'n_estimators': randint(50, 200),
'max_depth': randint(3, 10),
'min_samples_split': randint(2, 10)
}
random_search = RandomizedSearchCV(RandomForestClassifier(), param_distributions=param_dist, n_iter=10, cv=5)
random_search.fit(X_train, y_train)
print("Best Parameters:", random_search.best_params_)
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๐ง Tips for Effective Tuning
-
Start small, then zoom in on promising ranges
-
Use cross-validation for stable results
-
Prefer RandomizedSearchCV for large parameter spaces
-
Use automated tools like Optuna or Hyperopt for advanced tuning
๐ Summary: Model Evaluation & Tuning Workflow
-
Evaluate basic performance (accuracy, precision, recall, etc.)
-
Use cross-validation to reduce variance
-
Detect overfitting with learning curves
-
Tune hyperparameters using Grid or Random Search
-
Compare models and pick the best one
๐ Final Thoughts
Model evaluation and tuning isn't just about improving numbers — it's about building a model that can adapt to unseen real-world data.
This process helps you go from a "working model" to a "production-ready model".
๐ Section 8: Model Deployment & Monitoring
After you've trained, evaluated, and tuned your machine learning model, the next step is to deploy it into the real world — so users, applications, or systems can interact with it. Deployment isn't the end — continuous monitoring is required to ensure performance doesn’t degrade over time.
✅ 8.1 What is Model Deployment?
Model deployment is the process of integrating a trained ML model into a production environment where it can make real-time or batch predictions.
Goals:
-
Make your model available via a web app, API, or batch service
-
Connect it to real-world input sources
-
Serve predictions to users or applications
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๐ง 8.2 Ways to Deploy a Model
๐ 1. Web App Interface
Build a user interface (UI) that accepts input and shows prediction.
-
Tools: Flask, Django, Streamlit, Gradio
-
Example:
# Flask example
from flask import Flask, request, jsonify
import pickle
app = Flask(__name__)
model = pickle.load(open('model.pkl', 'rb'))
@app.route('/predict', methods=['POST'])
def predict():
data = request.json['features']
prediction = model.predict([data])
return jsonify({'prediction': prediction.tolist()})
⚙️ 2. REST API
Expose model predictions as endpoints.
-
Tools: Flask API, FastAPI, Django Rest Framework
-
Integrates well with mobile/web/other systems
☁️ 3. Cloud Services
Use cloud platforms to scale and deploy.
-
AWS SageMaker
-
Google AI Platform
-
Azure ML
-
Supports model versioning, A/B testing, monitoring
๐ฅ️ 4. Batch Deployment
Used for offline predictions (e.g., scoring millions of records nightly).
-
Schedule model runs using Airflow, cron, or Cloud Functions
๐ฆ 8.3 Saving and Loading Models
Before deployment, save your model:
✅ For Scikit-learn:
import pickle
# Save
pickle.dump(model, open('model.pkl', 'wb'))
# Load
model = pickle.load(open('model.pkl', 'rb'))
✅ For TensorFlow/Keras:
model.save('my_model.h5')
model = keras.models.load_model('my_model.h5')
๐ 8.4 Monitoring Deployed Models
Even after deployment, model performance may drift. Reasons:
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Data Drift: Input data changes
-
Concept Drift: Real-world patterns change
๐ง Monitor:
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Prediction accuracy and user feedback
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Input/output distribution shifts
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Model latency and failure rates
๐ Tools:
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Prometheus + Grafana
-
MLflow
-
EvidentlyAI (for drift detection)
⚖️ 8.5 Versioning & Re-training
Always version your:
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Dataset
-
Model code
-
Model weights
When model accuracy drops:
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Retrain with fresh data
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Re-tune hyperparameters
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Re-deploy the updated model
๐ Summary: ML Deployment & Monitoring Workflow
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Save and package the model
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Deploy via web app, API, or cloud service
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Enable input/output validation
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Monitor prediction quality and performance
➕ What’s Next?
In the next section (Section 9), you might cover:
-
๐ ML Pipelines & Automation
-
⛓️ MLOps: Managing end-to-end ML lifecycle
-
๐ CI/CD for Machine Learning
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๐ ️ Section 9: ML Pipelines & MLOps
Machine Learning is more than building and deploying models — it's about managing the entire lifecycle efficiently. As projects grow, you need automation, version control, and collaboration. That’s where ML Pipelines and MLOps come in.
✅ 9.1 What is a Machine Learning Pipeline?
A Machine Learning pipeline is a sequence of automated steps that process data, train a model, evaluate it, and optionally deploy it.
๐ Typical Pipeline Stages:
-
Data Ingestion – Load raw data
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Data Cleaning & Preprocessing – Handle missing values, encode data
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Feature Engineering – Extract useful patterns
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Model Training – Use algorithms to learn patterns
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Evaluation – Test model accuracy
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Tuning – Hyperparameter optimization
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Deployment – Send model to production
-
Monitoring – Track real-world performance
๐งช Code Example: Using Pipeline
in scikit-learn
from sklearn.pipeline import Pipeline
from sklearn.preprocessing import StandardScaler
from sklearn.ensemble import RandomForestClassifier
pipeline = Pipeline([
('scaler', StandardScaler()),
('model', RandomForestClassifier(n_estimators=100))
])
pipeline.fit(X_train, y_train)
y_pred = pipeline.predict(X_test)
Pipelines help avoid data leakage and ensure reproducibility.
⚙️ 9.2 What is MLOps?
MLOps (Machine Learning Operations) is the ML equivalent of DevOps. It’s a set of practices for automating and managing the ML lifecycle.
๐งฐ MLOps Covers:
-
Versioning (code, data, model)
-
Automation (training, testing, deployment)
-
Monitoring (drift, accuracy)
-
Collaboration (between data scientists & engineers)
๐ Tools in the MLOps Stack:
Purpose | Tools |
---|---|
Workflow Orchestration | Kubeflow, Airflow, Prefect |
Experiment Tracking | MLflow, Weights & Biases |
Deployment | Docker, FastAPI, Flask, TensorFlow Serving |
Monitoring | Prometheus, Grafana, EvidentlyAI |
CI/CD for ML | GitHub Actions, Jenkins, DVC, MLflow |
๐ 9.3 CI/CD for Machine Learning
Just like software, ML should support:
-
Continuous Integration (CI): Test model code regularly
-
Continuous Delivery (CD): Deploy updated models automatically
Example Flow:
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New data is pushed → triggers training pipeline
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Model is evaluated
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If performance passes threshold → auto-deployed
-
Logs and performance tracked
๐ก Tools:
-
GitHub Actions + Docker for automation
-
DVC (Data Version Control) to track data changes
-
MLflow for experiment tracking & model registry
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๐ 9.4 Reproducibility & Versioning
Reproducibility means your experiments can be run again and again with the same results.
Version:
-
Code (using Git)
-
Data (using DVC)
-
Models (with timestamps or hash IDs)
-
Experiments (use MLflow, W&B)
# Example with DVC
dvc init
dvc add data.csv
git add data.csv.dvc .gitignore
git commit -m "Track data with DVC"
๐ฆ 9.5 Putting It All Together: Example MLOps Pipeline
Use Case: Predicting customer churn
-
Data engineer uploads new data → versioned with DVC
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GitHub Actions triggers training pipeline
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Model is trained, evaluated
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Best model pushed to model registry (MLflow)
-
FastAPI or Flask deploys the model as a REST API
-
Grafana monitors latency, performance, and data drift
๐ง 9.6 Benefits of MLOps
Benefit | Explanation |
---|---|
๐ Faster Development | Automate repetitive tasks |
๐ Better Accuracy | Re-train with new data easily |
๐งช Reproducibility | Same results every time |
๐ Continuous Delivery | Automatically push new models to production |
๐ Monitoring | Catch drift and errors before it impacts users |
๐ Summary: Pipelines & MLOps Workflow
-
Break your ML workflow into repeatable steps
-
Automate with tools like scikit-learn Pipelines, Airflow
-
Track experiments, data, and models
-
Use MLOps tools to automate deployment and monitoring
-
Build a production ML system that’s robust, scalable, and auditable
๐ Final Thoughts
MLOps and Pipelines transform your ML process from a notebook experiment to a scalable, production-grade solution. It ensures your model keeps improving, even after deployment — making your ML system future-proof.
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