Distributed learning automata for solving a classification task

Abstract

In this paper, we propose a novel classifier in two-dimensional feature spaces based on the theory of Learning Automata (LA). The essence of our scheme is to search for a separator in the feature space by imposing a LA based random walk in a grid system. To each node in the gird we attach an LA, whose actions are the choice of the edges forming the separator. The walk is self-enclosing, i.e, a new random walk is started whenever the walker returns to starting node forming a closed classification path yielding a many edged polygon. In our approach, the different LA attached at the different nodes search for a polygon that best encircles and separates each class. Based on the obtained polygons, we perform classification by labelling items encircled by a polygon as part of a class using ray casting function. From a methodological perspective, PolyLA has appealing properties compared to SVM. In fact, unlike PolyLA, the SVM performance is dependent on the right choice of the kernel function (e.g. Linear Kernel, Gaussian Kernel) — which is considered a “black art”. PolyLA can find arbitrarily complex separator in the feature space. Experimental results show that our scheme is able to perfectly separate both simple and complex patterns outperforming existing classifiers, such as polynomial and linear SVM, without the need of a “kernel trick”. We believe that the results are impressive given the simplicity of PolyLA compared to other approaches such as SVM.