Feature subset generation

A feature selection process mainly consists of two parts feature subset generation and feature subset evaluation. Feature subset generation is a searching procedure. It generates subsets of features for... 

In this chapter, we will recommend two new kinds of feature selection methods for chemical data processing. One is SVM-BFS method, and another is SVM-RFE method. Both of them are based on advanced feature subset generation techniques and the criterion of generalization ability contribution of features. 

Floating search method proposed by Pudil et al. [112] is used as feature subset generation procedure, and has been proved to be one of the best subset generation algorithms for moderately large or small data sets. Backward floating search (BFS) method needs more computer time than forward floating search method, but it can treat interactive features well, so we combine it with SVM based on wrapper method and name it SVM-BFS method. 

Feature-selection techniques can be generally considered as a combination of both a search algorithm and a criterion function. The solution to feature-selection problem is offered by the search algorithm, which generates a subset of features and compares them on the basis of the criterion function. From a computational viewpoint, an exhaustive search for the optimal solution becomes intractable even for moderate values of features (Siedlecki and Sklansky 1988). Despite these apparent difficulties, many feature-selection approaches have been developed (Serpico and Bruzzone 1994). The sequential forward selection (SFS) and the sequential backward selection (SBS) techniques are the simplest suboptimal search strategies they can identify the best feature subset achievable by adding (to an empty set in SFS) or removing (from the complete set from SBS) one feature at a time, until the desired number of features is achieved. 

Control of cytokine release by CD8 T cells shares some features with CD4 T cells, although there is no direct correlation between CD8 subsets and ThI and Th2 cell subsets. Mouse CD8 spleen cells cultured with IL-2, IL-4 and anti-CD3 antibodies produce large amounts of IL-4 (Seder et al., 1992). Rat CD8" T cells cultured with Con A, IL-2, IL-4 and anti-IFN7 generate increased amounts of IL-4 and IU5 mRNA when restimulated with phorbol myristate acetate (PMA) and ionomycin (Noble, MacAry and Kemeny, 1995). However, in contrast to Th2 cells, most alloreac-... 

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