我在运行这个 plm 模型时遇到问题:
我的数据是(示例):
country=c(1,1,1,2,2,2,3,3,3)
year=c(1,2,3,1,2,3,1,2,3)
a=c(1,4,6,3,5,8,4,5,7)
b=c(8,5,7,2,7,4,9,7,1)
matrix=cbind(country, year, a, b)
matrix=plm.data(matrix)
我运行以下回归:
reg=plm(a~year+b, data=matrix, index=NULL, model="within")
summary(reg)
并收到以下警告消息:[1]
Warning messages:
1: In if (is.na(le)) { :
the condition has length > 1 and only the first element will be used
2: In if (is.na(le)) " __no length(.)__ " else if (give.length) { :
the condition has length > 1 and only the first element will be used
3: In if (le > 0) paste0("[1:", paste(le), "]") else "(0)" :
the condition has length > 1 and only the first element will be used
怎么了?