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Proximal Support Vector Machine Classifiers KDD 2001 San Francisco August 26-29, 2001. Glenn Fung & Olvi Mangasarian. Data Mining Institute University of Wisconsin - Madison. Support Vector Machines Maximizing the Margin between Bounding Planes. A+. A-.
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Proximal Support Vector Machine ClassifiersKDD 2001San Francisco August 26-29, 2001 Glenn Fung & Olvi Mangasarian Data Mining Institute University of Wisconsin - Madison
Support Vector MachinesMaximizing the Margin between Bounding Planes A+ A-
Proximal Vector MachinesFitting the Data using two parallel Bounding Planes A+ A-
Solve the quadratic program for some : min (QP) , s. t. where , denotes or membership. • Marginis maximized by minimizing Standard Support Vector Machine Formulation
min (QP) s. t. Solving for in terms of and gives: min PSVM Formulation We have from the QP SVM formulation: This simple, but critical modification, changes the nature of the optimization problem tremendously!!
Advantages of New Formulation • Objective function remains strongly convex • An explicit exact solution can be written in terms of the problem data • PSVM classifier is obtained by solving a single system of linear equations in the usually small dimensional input space • Exact leave-one-out-correctness can be obtained in terms of problem data
We want to solve: min Linear PSVM • Setting the gradient equal to zero, gives a nonsingular system of linear equations. • Solution of the system gives the desired PSVM classifier
Here, • The linear system to solve depends on: which is of the size is usually much smaller than Linear PSVM Solution
Input Define Calculate Solve Classifier: Linear Proximal SVM Algorithm
Linear PSVM: (Linear separating surface: ) : min (QP) s. t. . Maximizing the margin By QP “duality”, in the “dual space” , gives: min min • Replace by a nonlinear kernel Nonlinear PSVM Formulation
The nonlinear classifier: : • Gaussian (Radial Basis) Kernel • The represents the “similarity” -entryof of data points and The Nonlinear Classifier • Where K is a nonlinear kernel, e.g.:
Similar to the linear case, setting the gradient equal to zero, we obtain: Defining slightly different: • Here, the linear system to solve is of the size Nonlinear PSVM However, reduced kernels techniques can be used (RSVM) to reduce dimensionality.
Input Define Calculate Classifier: Classifier: Linear Proximal SVM Algorithm Non Solve