请问input中@和@@有什么区别啊？

shiyiming

INPUT Type $ @;
IF Type = ’surface’ THEN DELETE;


INPUT City $ State $ NormalRain MeanDaysRain @@;

shiyiming

Line-Hold Specifiers

@
(trailing @) prevents SAS from automatically reading a new data record into the input buffer when a new INPUT statement is executed within the same iteration of the DATA step. When used, the trailing @ must be the last item in the INPUT statement.

@@
(double trailing @) prevents SAS from automatically reading a new data record into the input buffer when the next INPUT statement is executed, even if the DATA step returns to the top for another iteration. When used, the double trailing @ must be the last item in the INPUT statement.

一般来说，差别不是很大，只是习惯上@下面还有根另外一个input，以便根据上面的内容进行判断怎么去读下一条记录。而@@则习惯于连续的读取一行的记录，对于不喜欢断行的人来说挺好用。总之，看你一行的内容是不是就是你要读入的变量，是的话两者没有差别，不是的话，稍有用途的差别。

shiyiming

多谢了，

shiyiming

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