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Relevance vector machine

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Machine learning technique
Part of a series on
Machine learning
anddata mining

Inmathematics, aRelevance Vector Machine (RVM) is amachine learning technique that usesBayesian inference to obtainparsimonious solutions forregression andprobabilistic classification.[1] A greedy optimisation procedure and thus fast version were subsequently developed.[2][3]The RVM has an identical functional form to thesupport vector machine, but provides probabilistic classification.

It is actually equivalent to aGaussian process model withcovariance function:

k(x,x)=j=1N1αjφ(x,xj)φ(x,xj){\displaystyle k(\mathbf {x} ,\mathbf {x'} )=\sum _{j=1}^{N}{\frac {1}{\alpha _{j}}}\varphi (\mathbf {x} ,\mathbf {x} _{j})\varphi (\mathbf {x} ',\mathbf {x} _{j})}

whereφ{\displaystyle \varphi } is thekernel function (usually Gaussian),αj{\displaystyle \alpha _{j}} are the variances of the prior on the weight vectorwN(0,α1I){\displaystyle w\sim N(0,\alpha ^{-1}I)}, andx1,,xN{\displaystyle \mathbf {x} _{1},\ldots ,\mathbf {x} _{N}} are the input vectors of thetraining set.[4]

Compared to that ofsupport vector machines (SVM), the Bayesian formulation of the RVM avoids the set of free parameters of the SVM (that usually require cross-validation-based post-optimizations). However RVMs use anexpectation maximization (EM)-like learning method and are therefore at risk of local minima. This is unlike the standardsequential minimal optimization (SMO)-based algorithms employed bySVMs, which are guaranteed to find a global optimum (of the convex problem).

The relevance vector machine waspatented in the United States byMicrosoft (patent expired September 4, 2019).[5]

See also

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References

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  1. ^Tipping, Michael E. (2001)."Sparse Bayesian Learning and the Relevance Vector Machine".Journal of Machine Learning Research.1:211–244.
  2. ^Tipping, Michael; Faul, Anita (2003)."Fast Marginal Likelihood Maximisation for Sparse Bayesian Models".Proceedings of the Ninth International Workshop on Artificial Intelligence and Statistics:276–283. Retrieved21 November 2024.
  3. ^Faul, Anita; Tipping, Michael (2001)."Analysis of Sparse Bayesian Learning"(PDF).Advances in Neural Information Processing Systems. Retrieved21 November 2024.
  4. ^Candela, Joaquin Quiñonero (2004). "Sparse Probabilistic Linear Models and the RVM".Learning with Uncertainty - Gaussian Processes and Relevance Vector Machines(PDF) (Ph.D.). Technical University of Denmark. RetrievedApril 22, 2016.
  5. ^US 6633857, Michael E. Tipping, "Relevance vector machine" 
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