kernlab: couple – R documentation

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couple

Probabilities Coupling function

Description

couple is used to link class-probability estimates produced by pairwise coupling in multi-class classification problems.

Usage

couple(probin, coupler = "minpair")

Arguments

`probin`	The pairwise coupled class-probability estimates
`coupler`	The type of coupler to use. Currently `minpar` and `pkpd` and `vote` are supported (see reference for more details). If `vote` is selected the returned value is a primitive estimate passed on given votes.

Details

As binary classification problems are much easier to solve many techniques exist to decompose multi-class classification problems into many binary classification problems (voting, error codes, etc.). Pairwise coupling (one against one) constructs a rule for discriminating between every pair of classes and then selecting the class with the most winning two-class decisions. By using Platt's probabilities output for SVM one can get a class probability for each of the k(k-1)/2 models created in the pairwise classification. The couple method implements various techniques to combine these probabilities.

Value

A matrix with the resulting probability estimates.

Author(s)

Alexandros Karatzoglou
alexandros.karatzoglou@ci.tuwien.ac.at

References

Ting-Fan Wu, Chih-Jen Lin, ruby C. Weng
Probability Estimates for Multi-class Classification by Pairwise Coupling
Neural Information Processing Symposium 2003
http://books.nips.cc/papers/files/nips16/NIPS2003_0538.pdf

Examples

## create artificial pairwise probabilities
pairs <- matrix(c(0.82,0.12,0.76,0.1,0.9,0.05),2)

couple(pairs)

couple(pairs, coupler="pkpd")

couple(pairs, coupler ="vote")

kernlab

Kernel-Based Machine Learning Lab

v0.9-29

GPL-2

Authors

Alexandros Karatzoglou [aut, cre], Alex Smola [aut], Kurt Hornik [aut], National ICT Australia (NICTA) [cph], Michael A. Maniscalco [ctb, cph], Choon Hui Teo [ctb]

Initial release