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发帖数: 638 | 1 都是关于index的..发现自己只要是关于index的题,都是全军覆没.
1 To create a dataset with unique values of
a given varible using a data step and the
FIRST. and LAST. varaibales, it is assumed
that the input dataset is:
A.
sorted on that variable.
B.
indexed by that variable.
C.
naturally in order.
D.
any of the above A, B, or C
这个答案是A,我咋觉得AB都行啊.谁知道能给解释一下吗.
2. The SAS data set WORK.TEST has an index
on the variable Id and the following SAS
program is submitted.
data WORK.TEST;
set WORK.TEST(
keep=Id Var_1 Var_2
rename=(Id=Id_Code));
Total=sum(Var_1, Var_2);
run;
Which describes the result of
submitting the SAS program?
A.
The index on Id is deleted.
B.
The index on Id is updated as an index on Id_Code.
C.
The index on Id is deleted and an index on Id_Code is created.
D.
The index on Id is recreated as an index on Id_Code.
答案是A.
这个答案我老觉得有点故意设局的感觉.
答案是A的话,是说明index本身被删除了,还是对应的index file也给删掉了呢? 如果是
前者,
是不是说明只是删除了index,但是相应的index file给id_code了?
如果是后者,那岂不是还要给id_code重建一个index file呢?
谁能给解释一下吗? 或者online tutor里有什么东西我给漏看了?
谢谢啦. |
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