标题: 求助一个困饶了我很久的问题!!!! [打印本页] 作者: shiyiming 时间: 2007-9-27 12:13 标题: 求助一个困饶了我很久的问题!!!! 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.作者: shiyiming 时间: 2007-9-27 14:22 标题: Re: 求助一个困饶了我很久的问题!!!! 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.作者: shiyiming 时间: 2007-9-28 11:02 标题: Re: 求助一个困饶了我很久的问题!!!! 谢谢!!!1