我在用stata做多年度的回归分析,想用面板数据来做,用xtset命令设置面板数据的维度时出现错误
我输入的命令式:
xtset code year
出现以下错误
error . . . . . . . . . . . . . . . . . . . . . . . . Return code 109
type mismatch;
In an expression, you attempted to combine a string and numeric
subexpression in a logically impossible way. For instance, you
attempted to subtract a string from a number or you attempted
to take the substring of a number.
(end of search)
应该怎么解决,急求