数据预处理 center&scale&box-cox http://stackoverflow.com/questions/33944129/python-library-for-data-scaling-centering-and-box-cox-transformation http://shahramabyari.com/2015/12/20/data-preparation-for-predictive-modeling-centering-scaling/ https://stats.stackexchange.com/questions/29781/when-conducting-multiple-regression-when-should-you-center-your-predictor-varia