求助一个困饶了我很久的问题!!!!

shiyiming

我一直不是很清楚retain语句的用法,特别是在DATA步中SET语句时,如果再加上一个循环,我就找不着北了.
经常和赋值语句混用,不知道他们的区别.
比如:
RETAIN VAR 0;
VAR=0;
这两个语句有什么区别啊?能否举个简单的例子?
各位大侠能否指点一二啊.

shiyiming

RETAIN causes a variable that is created by an INPUT or assignment statement to retain its value from one iteration of the DATA step to the next.
Without a RETAIN statement, SAS automatically sets variables that are assigned values by an INPUT or assignment statement to missing before each iteration of the DATA step.

So if 'var' is a new variable for the dataset(s) read from set statement, results of the two statment are the same. But if 'var' has existed in the dataset(s), the results will be distinct.

shiyiming

谢谢!!!1