SAS Chapter 11 Creating And Managing Variables

1. Which of the following can determine the length of a new variable?

The length of the variable's first value

The assignment statement

The LENGTH statement

All of the above

The length of a variable is determined by its first reference in the DATA step. When creating a new character variable, SAS allocates as many bytes of storage space as there are characters in the first value that it encounters for that variable. The first reference to a new variable can also be made with a LENGTH statement or an assignment statement. The length of the variable's first value does not matter once the variable has been referenced in your program.

Explanation

The length of a variable is determined by its first reference in the DATA step. When creating a new character variable, SAS allocates as many bytes of storage space as there are characters in the first value that it encounters for that variable. The first reference to a new variable can also be made with a LENGTH statement or an assignment statement. The length of the variable's first value does not matter once the variable has been referenced in your program.

2. Which set of statements is equivalent to the code shown below? if code='1' then Type='Fixed'; if code='2' then Type='Variable'; if code^='1' and code^='2' then Type='Unknown';

If code='1' then Type='Fixed';else if code='2' then Type='Variable';else Type='Unknown';

If code='1' then Type='Fixed';if code='2' then Type='Variable';else Type='Unknown';

If code='1' then type='Fixed';else code='2' and type='Variable';else type='Unknown';

If code='1' and type='Fixed';then code='2' and type='Variable';else type='Unknown';

You can write multiple ELSE statements to specify a series of mutually exclusive conditions. The ELSE statement must follow the IF-THEN statement in your program. An ELSE statement executes only if the previous IF-THEN/ELSE statement is false.

Explanation

You can write multiple ELSE statements to specify a series of mutually exclusive conditions. The ELSE statement must follow the IF-THEN statement in your program. An ELSE statement executes only if the previous IF-THEN/ELSE statement is false.

3. Now consider the revised program below. What is the value of Count after the third observation is read?

Missing

0

100

130

The RETAIN statement assigns an initial value of 100 to the variable Count, so the value of Count in the third observation would be 100+10+20+0, or 130.

Explanation

The RETAIN statement assigns an initial value of 100 to the variable Count, so the value of Count in the third observation would be 100+10+20+0, or 130.

4. How is the variable Amount labeled and formatted in the PROC PRINT output? data credit;
infile creddata;
input Account $ 1-5 Name $ 7-25 Type $27
Transact $ 29-35 Amount 37-50;
label amount='Amount of Loan';
format amount dollar 12.2;
run;
proc print data=credit label;
label amount='Total Amount Loaned';
format amount comma10.;
run;

Label Amount of Loan, format DOLLAR12.2

Label Total Amount Loaned, format COMMA10.

Label Amount, default format

The PROC PRINT step does not execute because two labels and two formats are assigned to the same variable.

The variable Amount is labeled as "Total Amount Loaned" and formatted as "COMMA10." in the PROC PRINT output.

Explanation

The variable Amount is labeled as "Total Amount Loaned" and formatted as "COMMA10." in the PROC PRINT output.

5. What is the length of the variable Type, as created in the DATA step below? data finance.records; set finance.records; TotLoan+payment; if code='1' then Type='Fixed'; else Type='Variable'; length type $ 10; run;

5

8

10

It depends on the first value of Type

The length of a new variable is determined by the first reference in the DATA step, not by data values. In this case, the length of Type is determined by the value Fixed. The LENGTH statement is in the wrong place; it must be read before any other reference to the variable in the DATA step. The LENGTH statement cannot change the length of an existing variable.

Explanation

The length of a new variable is determined by the first reference in the DATA step, not by data values. In this case, the length of Type is determined by the value Fixed. The LENGTH statement is in the wrong place; it must be read before any other reference to the variable in the DATA step. The LENGTH statement cannot change the length of an existing variable.

6. Consider the small raw data file and program shown below. What is the value of Count after the fourth record is read?

Missing

0

30

70

The sum statement adds the result of the expression that is on the right side of the plus sign to the numeric variable that is on the left side. The new value is then retained for subsequent observations. The sum statement treats the missing value as a 0, so the value of Count in the fourth observation would be 10+20+0+40, or 70.

Explanation

The sum statement adds the result of the expression that is on the right side of the plus sign to the numeric variable that is on the left side. The new value is then retained for subsequent observations. The sum statement treats the missing value as a 0, so the value of Count in the fourth observation would be 10+20+0+40, or 70.

7. Consider the IF-THEN statement shown below. When the statement is executed, which expression is evaluated first? if finlexam>=95 and (research='A' or (project='A' and present='A')) then Grade='A+';

Finlexam>=95

Research='A'

Project='A' and present='A'

Research='A' or(project='A' and present='A')

Logical comparisons that are enclosed in parenthesis are evaluated as true or false before they are compared to other expressions. In the example above, the AND comparison within the nested parenthesis is evaluated before being compared to the OR comparison.

Explanation

Logical comparisons that are enclosed in parenthesis are evaluated as true or false before they are compared to other expressions. In the example above, the AND comparison within the nested parenthesis is evaluated before being compared to the OR comparison.

8. Which program creates the output shown below?

Program c correctly deletes the observation in which the value of Finish is oak and the value of Price is less than 200. It also creates TotalPrice by summing the variable Price down observations, then drops Price by using the DROP= data set option in the DATA statement.

Explanation

Program c correctly deletes the observation in which the value of Finish is oak and the value of Price is less than 200. It also creates TotalPrice by summing the variable Price down observations, then drops Price by using the DROP= data set option in the DATA statement.

9. For the observation show below, what is the result of the IF-THEN statements?

if status='OK' and type=3 then Count+1; if status='S' or action='E' then Control='Stop';

Count = 12 Control = Go

Count = 13 Control = Stop

Count = 12 Control = Stop

Count = 13 Control = Go

You must enclose character values in quotation marks, and you must specify them in the same case in which they appear in the data set. The value ok is not identical to OK, so the value of Count i snot changed by the IF-THEN statement.

Explanation

You must enclose character values in quotation marks, and you must specify them in the same case in which they appear in the data set. The value ok is not identical to OK, so the value of Count i snot changed by the IF-THEN statement.

10. Which program contains an error?

Proc print data=clinic.stress; label totaltime='Total Duration of Test'; format timemin 5.2; drop sumsec;run;

Proc print data=clinic.stress(keep=totaltime timemin); label totaltime='Total Duration of Test'; format timemin 5.2;run;

To select variables, you can use a DROP or KEEP statement in any DATA step. You can also use the DROP= or KEEP= data set options following a data set name in any DATA or PROC step. However, you cannot use DROP or KEEP statements in PROC steps.

Explanation

To select variables, you can use a DROP or KEEP statement in any DATA step. You can also use the DROP= or KEEP= data set options following a data set name in any DATA or PROC step. However, you cannot use DROP or KEEP statements in PROC steps.