Kickstart ML with Python snippets
Getting started with machine learning models
Machine Learning Algorithms are a set of mathematical models and statistical techniques that enable computers to learn from data and make predictions or decisions without being explicitly programmed to perform those tasks. These algorithms improve their performance as they are exposed to more data over time.

Learning from Data:
 Machine learning algorithms analyze and identify patterns in historical data.
 They build models based on this data to make predictions or decisions about new, unseen data.

Types of Machine Learning:
 Supervised Learning: The algorithm is trained on a labeled
dataset, which means that each training example is paired with an output label.
The goal is to learn a mapping from inputs to outputs.
 Examples: Linear Regression, Decision Trees, Support Vector Machines (SVM).
 Unsupervised Learning: The algorithm is given data without
explicit instructions on what to do with it. The goal is to infer the natural
structure present within a set of data points.
 Examples: KMeans Clustering, Principal Component Analysis (PCA), DBSCAN.
 Reinforcement Learning: The algorithm learns by interacting
with an environment to achieve a goal. It receives rewards or penalties based on
its actions.
 Examples: QLearning, Deep QNetworks (DQN).
 Supervised Learning: The algorithm is trained on a labeled
dataset, which means that each training example is paired with an output label.
The goal is to learn a mapping from inputs to outputs.
Supervised vs. Unsupervised Learning vs. Reinforcement Learning
Supervised Learning
Supervised learning involves training a model on a labeled dataset. This means that for each training example, the model is provided with the input data and the corresponding correct output.
 Goal: Learn a mapping from inputs to outputs based on the provided labels.
 Applications: Commonly used when the goal is to predict specific outcomes.
 Example Tasks: Email spam detection, sentiment analysis, and house price prediction.
Key Concepts:
 Training Data: Contains both the input features and the labeled output.
 Labels: Known outcomes or target variables that the model tries to predict.
 Evaluation: Models are evaluated based on their ability to predict the correct labels on unseen data.
Example Algorithms:
 Classification: Logistic Regression, Support Vector Machines (SVM), Decision Trees, kNearest Neighbors (kNN), Random Forests.
 Regression: Linear Regression, Ridge Regression, Lasso Regression.
Unsupervised Learning
Unsupervised learning involves training a model on a dataset without labeled responses. The model tries to learn the underlying structure of the data based only on the input features.
 Goal: Discover hidden patterns or intrinsic structures in the input data.
 Applications: Commonly used for exploratory data analysis and dimensionality reduction.
 Example Tasks: Customer segmentation, anomaly detection, and market basket analysis.
Key Concepts:
 Training Data: Contains only the input features, without any labeled output.
 No Labels: The model does not know the correct outputs and tries to infer the structure from the data alone.
 Evaluation: Models are evaluated based on metrics that assess the quality of the discovered patterns or clusters.
Example Algorithms:
 Clustering: KMeans, Hierarchical Clustering, DBSCAN.
 Dimensionality Reduction: Principal Component Analysis (PCA), tDistributed Stochastic Neighbor Embedding (tSNE), Autoencoders.
Reinforcement Learning
Reinforcement learning involves training a model to make sequences of decisions by interacting with an environment. The model, often called an agent, learns to achieve a goal by receiving feedback in the form of rewards or penalties.
 Goal: Learn a strategy (policy) that maximizes the cumulative reward over time.
 Applications: Commonly used in robotics, gaming, and autonomous systems.
 Example Tasks: Game playing (e.g., AlphaGo), robotic control, and autonomous driving.
Key Concepts:
 Agent: The model that makes decisions.
 Environment: The external system the agent interacts with.
 Actions: The set of all possible moves or decisions the agent can make.
 State: The current situation of the agent within the environment.
 Reward: The feedback the agent receives from the environment after taking an action. It can be positive or negative.
 Policy: The strategy that the agent uses to determine the next action based on the current state.
 Value Function: A function that estimates the expected cumulative reward from a given state or stateaction pair.
Example Algorithms:
 ModelFree Methods: QLearning, Deep QNetworks (DQN), SARSA.
 PolicyBased Methods: REINFORCE, Proximal Policy Optimization (PPO), ActorCritic methods.
Groups of Machine Learning models
Classification (Supervised Learning)
Classification is a type of supervised learning where the goal is to assign inputs to one of several predefined categories or classes.

Examples:
 Spam detection (spam or not spam)
 Image recognition (cat, dog, or bird)
 Medical diagnosis (disease or no disease)

Key Features:
 Output: Categorical (discrete classes).
 Algorithms: Logistic regression, decision trees, random forests, support vector machines, neural networks.
Regression (Supervised Learning)
Regression is another type of supervised learning where the goal is to predict a continuous output variable based on input features.

Examples:
 Predicting house prices based on size, location, and other features.
 Forecasting stock prices.
 Estimating the amount of rainfall.

Key Features:
 Output: Continuous (realvalued).
 Algorithms: Linear regression, polynomial regression, ridge regression, lasso regression, neural networks.
Clustering (Unsupervised Learning)
Clustering is a type of unsupervised learning where the goal is to group similar data points together based on their features.

Examples:
 Customer segmentation (grouping customers based on purchasing behavior).
 Document clustering (grouping similar documents).
 Image compression (grouping similar pixels).

Key Features:
 Output: Groups or clusters of similar data points.
 Algorithms: Kmeans, hierarchical clustering, DBSCAN (DensityBased Spatial Clustering of Applications with Noise), Gaussian Mixture Models.
Differences
Learning Type  Supervised Learning  Unsupervised Learning 

Data  Labeled (inputoutput pairs)  Unlabeled (input only) 
Goal  Predict outcomes based on known labels  Discover hidden patterns or groupings 
Key Techniques  Classification, Regression  Clustering, Association 
Examples  Spam detection, house price prediction  Customer segmentation, anomaly detection 
Similarities
Group  Type  Description  Examples 

Classification  Supervised  Categorize inputs into predefined classes  Email spam detection, image recognition 
Regression  Supervised  Predict a continuous value  House price prediction, stock price forecasting 
Clustering  Unsupervised  Group similar data points together  Customer segmentation, document clustering 