基于SVDD的层次纠错输出编码研究

摘要

As a decomposing framework,error-correcting output codes (ECOC)can effectively reduce the multiclass to the binary and attract much attention,in which the construction of coding matrix based on data is the key to use ECOC to solve multiclass problems.An approach of hierarchical error-correcting output codes (HE-COC)based on support vector domain description (SVDD)and Fisher theory is presented.Firstly,the SVDD is used to measure the class separabilty quantitatively.Then the inter-class separability matrix is got gradually. The binary tree is built based on the matrixes from the bottom to the top.Then,each node of the binary tree is encoded by the level to get the final HECOC.The separability of base classifiers trained by different class parti-tion is compared in experiments.The results show that the HECOC can promote the diversity of the base classi-fiers and the error-correcting ability of codewords as well as enhance the classification accuracy.%纠错输出编码能有效地将多类问题分解为一系列二类子问题进行求解，已受到众多机器学习研究者的关注。如何构建基于数据的编码矩阵是编码方法确定的关键。针对此问题，基于Fisher原理，提出一种基于支持向量数据描述（support vector domain description，SVDD）的层次纠错输出编码构造方法（hierarchical error-correcting output codes， HECOC）。该方法首先采用SVDD计算各类别的可分程度，从而得到由不同子类构成的二叉树；然后分别对二叉树的各层结点进行编码并最终形成层次输出编码。在仿真实验中，对不同子类类群划分构成的基分类器的可分性进行了对比，结果表明，该编码方法能在保证分类精度的同时，提高基分类器之间的差异性和纠错输出编码的容错能力。