SAS Base (2)

Given the following raw data records in TEXTFILE.TXT:

----|----10---|----20---|----30
John,FEB,13,25,14,27,Final
John,MAR,26,17,29,11,23,Current
Tina,FEB,15,18,12,13,Final
Tina,MAR,29,14,19,27,20,Current

The following output is desired:

Obs Name Month Status Week1 Week2 Week3 Week4 Week5
1 John FEB Final $13 $25 $14 $27 .
2 John MAR Current $26 $17 $29 $11 $23
3 Tina FEB Final $15 $18 $12 $13 .
4 Tina MAR Current $29 $14 $19 $27 $20

Which SAS program correctly produces the desired output?

A.
data WORK.NUMBERS;

length Name $ 4 Month $ 3 Status $ 7;

infile ‘TEXTFILE.TXT’ dsd;

input Name $ Month $;

if Month=’FEB’ then input Week1 Week2 Week3 Week4 Status $;

else if Month=’MAR’ then input Week1 Week2 Week3 Week4 Week5 Status $;

format Week1-Week5 dollar6.;

run;

proc print data=WORK.NUMBERS;

run;

B.

data WORK.NUMBERS;

length Name $ 4 Month $ 3 Status $ 7;

infile ‘TEXTFILE.TXT’ dlm=’,’ missover;

input Name $ Month $;

if Month=’FEB’ then input Week1 Week2 Week3 Week4 Status $;

else if Month=’MAR’ then input Week1 Week2 Week3 Week4 Week5 Status $;

format Week1-Week5 dollar6.;

run;

proc print data=WORK.NUMBERS;

run;

C.

data WORK.NUMBERS;

length Name $ 4 Month $ 3 Status $ 7;

infile ‘TEXTFILE.TXT’ dlm=’,’;

input Name $ Month $ @;

if Month=’FEB’ then input Week1 Week2 Week3 Week4 Status $;

else if Month=’MAR’ then input Week1 Week2 Week3 Week4 Week5 Status $;

format Week1-Week5 dollar6.;

run;

proc print data=WORK.NUMBERS;

run;

D.

data WORK.NUMBERS;

length Name $ 4 Month $ 3 Status $ 7;

infile ‘TEXTFILE.TXT’ dsd @;

input Name $ Month $;

if Month=’FEB’ then input Week1 Week2 Week3 Week4 Status $;

else if Month=’MAR’ then input Week1 Week2 Week3 Week4 Week5 Status $;

format Week1-Week5 dollar6.;

run;

proc print data=WORK.NUMBERS;

run;

Check Answer
Answer: C

注解:

DSD:默认“,”为分隔符,将2个连续的分隔符视为一个missing value。比如将数据“a,b,,d”视为:’a’ ‘b’ missing value ‘d’

DLM:等价于DELIMITER,用于替换默认分隔符(空格)。比如DLM=’*’,将分隔符由空格替换成‘*’

MISSOVER:如果一行数据中的数据个数少于需要定义的变量数量,MISSOVER将防止SAS去下一行寻找数据,并将多出来的变量的值设为missing。比如,一行数据中仅有3个数据“a,b,c”,但INPUT中定义了4个变量(variable1-variable4)。如果没有MISSOVER,SAS会去新的一行寻找数据并为variable4赋值。加上MISSOVER,SAS就不会去下一行,而是将variable4的值设为missing。

@:默认情况下,每出现一次INPUT,SAS都会去新的一行读取数据,而@的作用是让SAS继续在当前行读取数据。比如这个例子:
data d1;
input v1 $ v2 $ @;
input v3 $ v4 $;
datalines;
a b c d
e f g h
;
run;
有@的输出为:

Obs v1 v2 v3 v4
1 a b c d
2 e f g h

去掉@则为:

Obs v1 v2 v3 v4
1 a b e f

与@类似的还有@@。区别在于,在同一个DATA步骤中阻止换行用@,而在不同的DATA步骤中则用@@。何为同一DATA步骤?上面这个例子中,声明了4个变量,那么定义一遍v1, v2, v3, v4为一个DATA步骤。下面举一个使用@@的例子:
data d2;
input v1 $ v2 $ @@;
datalines;
a b c d
;
run;
这个例子中定义一遍v1, v2为一个DATA步骤,@@能够阻止SAS在下一个DATA步骤中去新的一行读取数据。
有@@输出的结果为:

Obs v1 v2
1 a b
2 c d

不使用@或仅使用一个@的输出结果为:

Obs v1 v2
1 a b

3 thoughts on “SAS Base (2)

Leave a Reply

Your email address will not be published. Required fields are marked *