leffgh mode(dhs94.src$dbh) [1] "numeric" > mean(dhs94.src$dbh) [1] NA dhs94.src$dbh里有缺失值,原来记为*,后来我改为NA了,但是改不改求平均值都不成功. 望各位大侠指导,不胜感激. 本人刚开始学