kernlab (version 0.9-24)

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.

Value

A matrix with the resulting probability estimates.

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.

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

See Also

predict.ksvm, ksvm

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")