命令是:

library(plm)<br />
a<-read.csv("C:\\Users\\as4741\\Desktop\\lxx.csv")<br />
plm(CASH.ETR~EBIT+LEVERAGE,data=a,model=c("random"),<br />
    index=c("code","year"))
</p>

出现的错误是:duplicate couples (time-id)

错误于pdim.default(index[[1]], index[[2]]) :

请问是怎么回事儿啊?谢谢