请问利用bdiff命令去做分组回归系数比较的检验，总是出错
总是提示：not sorted

. local m "xtreg Wfassets6_mid L.MPU L.WVOX    i.quarter,fe r"


. bdiff, group(equity) model(`m') reps(100) bs first detail


Begin Time: 21 Nov 2020 16:10:16
not sorted
r(5);