Advanced Topic: Macro Processing

Question 1

Why do we use macro programming?

Answer 1

It allows us to make code more efficient. We can assing a name to a block of text, then just call it with the macro name, change code easily and make it flexible, reuse code over and over again.

Question 2

Define macro processor.

Answer 2

Translates macro statements into standard SAS statements

Question 3

Define a macro (program).

Answer 3

A sequence of DATA and PROC steps and macro-specific statements.

Question 4

Write the general syntax for macro varaibles.

Answer 4

%LET macro-name = value

Question 5

What are the rules for macro variable names?

Answer 5

1) can be up to 32 characters
2) Must start with a letter or underscore and contain only letters, underscores, or numbers

Question 6

What are the rules for macro variable values?

Answer 6

• Can be a variable name, a numeral, or text
• Can be over 65,000 characters long
• Does NOT require quotation marks even when it contains characters
• blanks at the beginning and end are trimmed
• Everything between the equal sign and the semicolon become part of the value for that variable

Question 7

What is the difference between global and local macros?

Answer 7

Global Macros: created outside of another macro. Can be used anywhere in the program.
Local Macros: created inside of macros and can only be used inside of the macro created

Question 8

How do you reference a macro?

Answer 8

Names must be preceded by the amperstand prefix (&) and followed by a period (.)
Ex. &flowertype.

Question 9

How do you resolve a macro?

resolve = replace it with a specific value

Answer 9

Enclose in DOUBLE quotation marks
Ex.
%LET country = US
countryname = “&Country.”; resolved to countryname = US;

Question 10

Explain the lines in the following code.

1) %LET flowertype = Ginger;
2) proc print data=flowersales;
3) where variety = “&flowertype.”;
format saleamount dollar7.0;
4) title “Sales of &flowertype.”;
run;

Answer 10

1) defines macro flowertype as “Ginger”
2) calls data from flowersales
3) Displays only from selected flowertype of “Ginger”
4) Displays title “Sales of Ginger”

Question 11

How do you delete a macro?

Answer 11

%SYMDEL macro-name

Question 12

List and describe 3 automatic macro variables.

Hint: All deal with date.

Answer 12

1) SYSDATE: the date of the SAS invocation (DATE7.0)
2) SYSDAY: the day of the week of the SAS invocation
3) SYSTIE: the time of the SAS invocation

Question 13

Write the general syntax for creating modular code.

Answer 13

%MACRO macro-name;
macro-text; (aka SAS statements)
%MEND macro-name;

Question 14

How do you invoke a macro moduler program?

Answer 14

%macro-name

Question 15

Explain the lines in the following code.

1) %MACRO Select (Customer=, SortVar=);
proc sort data=flowersales out = salesout;
2) by &SortVar.;
3) where customerid = “&customer.”;
run;
4) %MEND Select;
5) %Select (Customer = 356W, SortVar = SalesQuantity);

Answer 15

1) Creates macro Select with the parameters customer and sortvar
2) Sorts by value in sortvar
3) Selects customer in value of customerid
4) Tells SAS macro ends here
5) Runs macro with the parameters of customer = 356W and sortvar = salesquantity variable.

Question 16

Write the general syntax for conditional logic in macros.

Answer 16

%MACRO macro-name;
%IF condition %THEN %DO;
code-to-do;
%ELSE %IF condition %THEN %DO;
code-to-do;
%END;

Question 17

T/F: the %IF statement can contain actions that standard IF statements cannot. Such as complete DATA or PROC steps.

Answer 17

True

Question 18

Write the general syntax for iterative do loops in macros.

Answer 18

%DO macro-name = start-value %TO stop-value;
macro-text;
%END;

Question 19

T/F: The iterative %DO statement can be used in open SAS code.

Answer 19

False: Can only be used inside of macros.

Question 20

T/F: When the macro variable name is defined in the %DO statement, it does NOT start with an amperstand (&).

Answer 20

True, but do need to use it elsewhere outside of the %DO statement.

Question 21

What does CALL SYMPUTX do?

Answer 21

Takes a value from a data step and assigns it to a macro variable that can then be used later.

Question 22

Write the general syntax for CALL SYMPUTX.

Answer 22

CALL SYMPUTX (“macro-name”, value);

Question 23

List some macro functions that manipulate character strings

Answer 23

• %UPCASE
• %SUBSTR
• %INDEX
• %SCAN

Question 24

What does the %EVAL function do?

Answer 24

It evaluates arithmetic and logical expressions using integar arthmetic

Question 25

T/F: You can use non integers in the eval function.

Answer 25

False: only integers. Non-integers are truncated.
Ex. 8.5 => 8

Question 26

What does SYSFUNC do?

Answer 26

Executes SAS functions or user-defined functions in the macro facility

Question 27

What do the system options MERROR, SERROR, MLOGIC, MPRINT,and SYMBOLGEN do?

Answer 27

MERROR: issues a warning if you invoke a macro it cannot find
SERROR: issues a warning if you use a macro varaible it cannot find
MLOGIC: prints in log details about the execution of macro
MPRINT: prints in log the stadard SAS code generate by macros
SYMBOLGEN: prints in log the values of macro variables.

Question 28

T/F: By default, MERROR and SERROR are on and the others (MLOGIC, MPRINT, and SYMBOLGEN) are off.

Answer 28

True