local m "xtivreg2 out age  `dumind_provcd' `dumind_year' (abc = clean), cluster(pid2) fe"
bdiff, group(male) model(`m') reps(1000) bs first detail

Begin Time: 28 Aug 2023 22:12:18
....Warning: estimated covariance matrix of moment conditions not of full rank.
         overidentification statistic not reported, and standard errors and
         model tests should be interpreted with caution.
Possible causes:
         number of clusters insufficient to calculate robust covariance matrix
         singleton dummy variable (dummy with one 1 and N-1 0s or vice versa)
partial option may address problem.
..--Break--

这个问题困扰几天了，
同时尝试用手动自己写随机分组时总有问题，求问是否有方法可以在面板数据中随机指定数目的个体而不是观测值相应的取值为1吗？
第一次发帖，希望有好心人