此题貌似是说retain中不可以用array name  此题应该将retain monthsales{12}； 改为retain monthsales1-monthsales12；  array name只能用于duration of data step。  retian  keep drop中都不能直接用

base的书上是这样写的  cannot use array names in LAVEL,FORMAT,DROP,KEEP,or LENGTH statement.Arrays exist only for the duration of the DATA step,they don't become part of the output data set.
看来retain statement 也应该 can't use
谢谢你的解答