Semi-supervised Support Vector Machines (S3VM)
When we discussed the cluster assumption in the previous chapter, we also defined the low-density regions as boundaries and the corresponding problem as low-density separation. A common supervised classifier based on this concept is a Support Vector Machine (SVM), the objective of which is to maximize the distance between the dense regions where the samples must be.
S3VM Theory
For a complete description of linear and kernel-based SVMs, please refer to Bonaccorso G., Machine Learning Algorithms, Second Edition, Packt Publishing, 2018. However, it's useful to remind yourself of the basic model for a linear SVM with slack variables :
This model is based on the assumption that yi can be either -1 or 1. The slack variables or soft-margins are variables, one for each sample, introduced to reduce the strength imposed by the original condition (min ||w||), which is based on a hard margin that misclassifies...