Start by defining the business objective, the available data (labeled vs. unlabeled), and the evaluation metric that matters for the business (e.g., precision for fraud detection, MAE for demand forecasting). These three decisions usually determine the algorithm family you should evaluate first.
- Supervised learning
- Unsupervised learning
- Reinforcement learning

- Supervised learning: Trained on labeled examples (input → correct output). Typical tasks: classification and regression.
- Unsupervised learning: Works with unlabeled data to discover structure or latent representations — e.g., clustering and dimensionality reduction.
- Reinforcement learning: An agent interacts with an environment, learning policies that maximize cumulative reward (applications: robotics, recommendation engines, game AI).


Supervised Learning: Regression vs. Classification
Supervised learning problems split primarily into two categories:- Regression — predict continuous values (e.g., house prices, temperature).
- Classification — predict discrete labels (e.g., spam vs. not spam, disease vs. healthy).
- Linear Regression — linear mapping between inputs and output.
- Polynomial Regression — captures nonlinearity via higher-order terms.
- Ridge Regression — linear model with L2 regularization for robustness.
- Lasso Regression — L1 regularization that can produce sparse (feature-selecting) solutions.
- Decision Tree Regression — piecewise constant models via recursive splits.
- Random Forest Regression — ensemble of trees for better accuracy and stability.
- Gradient Boosting (e.g., XGBoost, LightGBM) — strong performance on tabular regression tasks.
- Binary classification — two classes (e.g., spam vs. not spam).
- Multi-class classification — one label from many mutually exclusive classes.
- Multi-label classification — multiple independent labels per instance.
- Ordinal classification — classes with a meaningful order (e.g., risk levels).
- Nominal classification — unordered categories.

Common model choices:

Be careful of common pitfalls: mislabeled training data, severe class imbalance, and data leakage. These issues can cause deceptively high training performance but poor real-world results.
Unsupervised Learning: Clustering and Beyond
Unsupervised learning extracts structure from unlabeled data. One of the most common tasks is clustering, which groups observations by similarity. Typical use cases include customer segmentation, product grouping, and behavioral profiling. Common clustering algorithms:- K-means — fast, centroid-based, assumes spherical clusters.
- Hierarchical clustering — builds nested clusters, useful for dendrograms.
- DBSCAN — density-based, identifies arbitrarily-shaped clusters and noise.
- Gaussian Mixture Models — probabilistic clusters with soft assignments.

Anomaly Detection
Anomaly detection identifies rare or unexpected events and is widely used in:- Credit card fraud detection
- Network intrusion detection
- Predictive maintenance (detect equipment failure)
- Medical anomaly detection
- Statistical thresholding and z-scores
- Isolation Forests — tree-based isolation for outliers
- One-Class SVM — boundary-based approach for normal data
- Autoencoders — reconstruction error flags anomalies
Practical Mapping Checklist
Use this checklist when mapping a business problem to algorithms:- Define the objective clearly (classification, regression, clustering, anomaly detection, policy optimization).
- Identify whether labeled data is available and its quality.
- Select evaluation metrics aligned with business impact (precision, recall, MAE, revenue-based metrics).
- Choose model families that suit data size, feature types, and interpretability needs.
- Prototype with simple baselines (logistic regression, decision trees) before moving to complex models.
- Monitor models in production for data drift, label shift, and performance degradation.
- Kubernetes Documentation (for model deployment patterns)
- Docker Hub (containerizing models)
- Scikit-learn (classical ML algorithms)
- XGBoost / LightGBM (gradient boosting implementations)