说明：  用LDA及pca算法分析特征，选择最好的特征。
(This program uses LDA and PCA to analyze features from weka arff file. The projection on PCA and LDA space visualizes the goodness of the features. If the features are good enough to be classified well they should have some kind of separation when projected on a 1 dimensional LDA or a 3 dimensional PCA space. This MATLAB script assumes that the arff file has 2 classes named "Positive" and "Negative". However, it can be extended into any amount of class labels. )