最大类间方差的基本思想是使用一个阈值将整个数据分成两个类，假如两个类之间的方差最大，那么这个阈值就是最佳的阈值-The between-cluster variance as the basic idea is to use a threshold to the whole data is divided into two classes, if the maximum variance between two classes, then the threshold value is the best threshold value