跟crakman做sas base认证试题（65）

shiyiming

From crackman's blog on Baidu


               
                <p><br>
<font size="4" face="宋体">67.Consider the following data step:<br>
<br>
  data WORK.NEW; <br>
&nbsp;&nbsp;&nbsp;&nbsp;  set WORK.OLD(keep=X);<br>
&nbsp;&nbsp;&nbsp;&nbsp;  if X &lt; 10 then X=1; <br>
&nbsp;&nbsp;&nbsp;&nbsp;  else if X &gt;= 10 AND X LT 20 then X=2; <br>
&nbsp;&nbsp;&nbsp;&nbsp;  else X=3;<br>
  run; <br>
<br>
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? </font></p>
<p><font size="4" face="宋体">&nbsp;&nbsp;&nbsp;&nbsp;  A. X would get a value of 1.<br>
&nbsp;&nbsp;&nbsp;&nbsp;  B. X would get a value of 3.<br>
&nbsp;&nbsp;&nbsp;&nbsp;  C. X would retain its original value of missing. <br>
&nbsp;&nbsp;&nbsp;&nbsp;  D. This step does not run because of syntax errors.</font></p>
<p><font size="4" face="宋体">Answer: A</font></p>
<p><font size="4" face="宋体">如果是缺失值，那么在排序过程中是默认为最小。<br>
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。</font></p>
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