我写的命令:
egen 年份 = group (year)
sem (a -> a1, ) (a -> a2, ) (a -> a3, ) (a -> a4, ) (a -> b, ) (a -> c, ) (b -> b1, ) (b ->b2, ) (b -> b3, ) (b -> b4, ) (b -> c, ) (c -> c1, ) (c -> c2, ) (c ->c3, ), method(mlmv) latent(a b c ), group (年份) ginvariant (none)
结果显示:invalid ‘group’
请问是我的命令有错误么?为什么显示 invalid ‘group’ 呢?