Self Organising Map (SOM)
Unit 4
          Dr. Sushil Kumar
         Associate Professor
Self-Organizing Map (SOM)
• A SOM is an unsupervised learning algorithm used for dimensionality reduction
  and data visualization.
• Developed by Teuvo Kohonen in 1982.
• SOMs are particularly effective in mapping high-dimensional data into lower-
  dimensional spaces (typically 2D) while preserving the topological structure of
  the input data.
• SOMs useful for clustering and pattern recognition tasks.
Key Features
1. Topology Preservation: Similar data points in the input space remain close to
   each other in the map.
2. Dimensionality Reduction: It reduces complex data into a simpler, visual
   representation.
3. Unsupervised Learning: SOMs learn without labeled data, discovering hidden
   patterns or structures.
Structure
Steps used in SOM
1.   Initialization
2.   Input Vector
3.   Best Matching Unit (BMU)
4.   Weight Update Rule
5.   Training Process
Initialization
Input Vector
Best Matching Unit (BMU)
Weight Update Rule
Training Process
Example:
Neighborhood Function
Weight Update Rule
Decay of Parameters