Unsupervised Learning

What is Unsupervised Learning?

Unsupervised learning is a type of machine learning where the model learns from a dataset without labeled output variables. The goal of unsupervised learning is to discover hidden patterns, structures, or relationships within the data. This type of learning is particularly useful for exploratory data analysis, keyword extraction, clustering, dimensionality reduction, and anomaly detection.

Unsupervised learning algorithms can be broadly classified into three categories:

  1. Clustering: Clustering algorithms group similar data points together based on their features, creating clusters or segments. Some popular clustering algorithms include K-means, hierarchical clustering, and DBSCAN.

  2. Dimensionality Reduction: Dimensionality reduction algorithms reduce the number of features in the dataset while preserving the most relevant information. This can help with visualization, noise reduction, and improving the performance of other machine learning models. Popular dimensionality reduction techniques include Principal Component Analysis (PCA), t-distributed Stochastic Neighbor Embedding (t-SNE), and autoencoders.

  3. Association rule: Association rule learning is commonly used in market basket analysis, recommendation systems, and other applications where finding relationships between items is important. In association rule learning, the goal is to identify rules or patterns that frequently occur together in the data. These rules are represented in the form of “if-then” statements, such as “If a customer buys item A, they are likely to buy item B as well.” The strength of these associations is typically measured using metrics such as support, confidence, and lift.

Reasons for using unsupervised learning:

  1. Unlabeled data: In many real-world scenarios, obtaining labeled data is expensive or time-consuming. Unsupervised learning can provide insights and reveal patterns in unlabeled data.

  2. Exploratory analysis: Unsupervised learning can help identify structures and relationships in the data, which is useful for hypothesis generation, feature engineering, and preparing data for supervised learning tasks.

  3. Complexity reduction: Dimensionality reduction techniques can simplify high-dimensional data, making it easier to analyze, visualize, and process.

Strategies for implementing unsupervised learning:

  1. Data preprocessing: Properly preprocessing the data, such as scaling, normalization, and handling missing values, is essential for the performance of unsupervised learning algorithms.

  2. Feature engineering: Creating new features and transforming existing features can enhance the ability of unsupervised learning algorithms to reveal patterns and relationships in the data.

  3. Hyperparameter tuning: Tuning the hyperparameters of unsupervised learning algorithms can improve the performance and robustness of the model.

More resources:

  1. Unsupervised learning tutorial with Keras

  2. Unsupervised learning with scikit-learn

  3. Clustering algorithm