1. Introduction
With the exponential growth of textual information available from the Internet, there has been an emergent need to find and organize relevant information in text collections. For this purpose, automatic text categorization becomes a significant tool to utilize text information efficiently and effectively. Text categorization aims to automatically place the documents on previously classes. It is an active research area in information retrieval, machine learning and natural language processing. At present there are many textual classification methods, such as the support vector machine (SVM), the Nearest Neighbor, the Decision Tree, the K Nearest Neighbor method (KNN) and others.