特征选择 RFormula RFormula是一个很方便,也很强大的Feature选择(自由组合的)工具. 输入string 进行独热编码(见下面例子country) 输入数值型转换为double(见下面例子hour) label为string,也用StringIndexer进行编号 RFormula produces a vector column of features and a double or string column of label. Like when formulas ar