在学习《Applied Econometrics with R》，GMM回归的代码结果提示错误：
> data("EmplUK",package="plm")
> form <- log(emp)~log(wage)+log(capital)+log(output)
> empl_ab <- pgmm(dynformula(form, list(2, 1, 0, 1)), data = EmplUK, index = c("firm", "year"), effect = "twoways", model = "twosteps", gmm.inst = ~ log(emp), lag.gmm = list(c(2, 99)))
Warning messages:
1: use of 'dynformula' is deprecated, use a multi-part formula instead
2: use of 'dynformula' is deprecated, use a multi-part formula instead


请问有大神会用R做GMM回归的吗？请教请教！！！