[img]file:///E:\Tencent Files\462590183\Image\C2C\QG[`Z%}]OFGUMJJVL(7[Z6X.png[/img][img=0,1]file:///E:\Tencent Files\462590183\Image\C2C\QG[`Z%}]OFGUMJJVL(7[Z6X.png[/img]希望各位大神指教，通过DEA计算生产率指数的四个方向距离函数各自代表什么意思呀