Probabilistic outputs for twin support vector machines

In many cases, the output of a classifier should be a calibrated posterior probability to enable post-processing. However, twin support vector machines (TWSVM) do not provide such probabilities. In this paper, we propose a TWSVM probability model, called PTWSVM, to estimate the posterior probability. Note that our model is quite different from the SVM probability model because of the different mechanism of TWSVM and SVM. In fact, for TWSVM, we first define a new ranking continues output by comparing the distances between the sample and the two non-parallel hyperplanes, and then map this ranking continues output into probability by training the parameters of an additional sigmoid function. Our PTWSVM has been tested on both artificial datasets and several data-mining-style datasets, and the numerical experiments indicate that PTWSVM yields nice results.