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标题: 跟crakman做sas base认证试题（65） [打印本页]

作者: shiyiming 时间: 2010-11-13 17:40
标题: 跟crakman做sas base认证试题（65）
From crackman's blog on Baidu

 
67.Consider the following data step: 
 
 data WORK.NEW; 
     set WORK.OLD(keep=X); 
     if X < 10 then X=1; 
     else if X >= 10 AND X LT 20 then X=2; 
     else X=3; 
 run; 
 
In filtering the values of the variable X in data set WORK.OLD, what value new value would be assigned to X if its original value was a missing value? 
     A. X would get a value of 1. 
     B. X would get a value of 3. 
     C. X would retain its original value of missing. 
     D. This step does not run because of syntax errors.
Answer: A
如果是缺失值，那么在排序过程中是默认为最小。 
大家可以用proc sort 过程来测试一组有缺失值的数据，就知道排在最小的观测的是缺失值。
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