Macro basics

Question 1

You can reference a macro variable anywhere is a SAS program except

Answer 1

in datalines

Question 2

When referencing a macro variable within a title, can you use both double and single quotation marks?

Answer 2

No, only double quotation marks. It won’t resolve in single quotation marks

Question 3

How do you display macro variable values in the SAS log using a system OPTION?

Answer 3

OPTIONS NOSYMBOLGEN/SYMBOLGEN;

It lists each macro variable and what it resolves to in the log.

Question 4

Tell me what %PUT does and 3 important things about it

Answer 4

%PUT allows you to write messages to the SAS log and resolve macro variables

1. writes only to the SAS log
2. does not require quotation marks around text
3. can be used either inside or outside a macro definition

Question 5

How do you list the values of all macro variables using %PUT?

all automatic variables?

all user-generated local variables?

all user-defined macro variables?

Answer 5

%put _all_

%put _automatic_

%put _local_

%put _user_

Question 6

What do macro quoting functions do?

Answer 6

Tell the macro processor to interpret special characters and mnemonics as text.

Question 7

%STR is most useful for character strings that contain

Answer 7

• A semicolon that should be treated as text
• blanks that are significant
• a quotation mark or parenthesis without a match

Question 8

%STR syntax for unmatched quotation mark, percent sign before a parenthesis and string with comment symbols

Answer 8

• %’ or %”, e.g. %str(Jim%’s office)
• %%) e.g. %str(20%%)
• %str(/)%str(*)comment text %str(*)%str(/)

Question 9

How are NR functions different than their non-NR friends?

Answer 9

They also mask % and &, so they prevent macro resolution.

Question 10

Use BQUOTE when

Answer 10

An expression has unmatching quotes

Question 11

Difference between %STR and %BQUOTE

Answer 11

%STR performs during compilation. %BQUOTE performs during execution.

%BQUOTE doesn’t require that unmatched quotation marks be marked with a %

Question 12

What function is like the %UPCASE function but also masks special characters and macro triggers?

Answer 12

%QUPCASE

Question 13

%SUBSTR function syntax

Answer 13

string is the text that you want to scan

%SUBSTR(string, position, n)

Question 14

What function is like the %SUBSTR function but also masks special characters and macro triggers?

Answer 14

%QSUBSTR

Question 15

What is the result of

%let a=one;
%let b=two;
%let c=%nrstr(&a &b);

%put &c;
%put %substr(&c, 1, 2);
%put %qsubstr(&c, 1, 2);

Answer 15

Note that for %substr, the substring it finds is &a (two characters) but then this resolves to the value of a.

%put &c: &a &b

%put %substr(&c, 1, 2); one

%put %qsubstr(&c, 1, 2); &a

Question 16

%INDEX function. What does it do and syntax

Answer 16

%INDEX(source, string)

It searches source for the first occurrence of string and returns a number representing the position in source of the first character of string (count by character)

Question 17

%SCAN function

Answer 17

%SCAN(string, n, delimiters)

Allows you to extract a word from a string

n is the position of the work to return

delimiters is optional

Question 18

%SCAN vs %QSCAN

Answer 18

%SCAN does not mask special characters or mnemonic operators in its result even when the argument was previously masked by a macro quoting function.

Question 19

%SYSFUNC and %QSYSFUNC

Answer 19

%SYSFUNC(function(arguments), format)

Allows you to use other SAS functions in the macro language

function is the name of the SAS function

arguments are arguments of the SAS function

format is optional

e.g.

%sysfunc(today(), weekdate.)

Friday, November 4, 2011

Question 20

What do you do if you want to have text right after a macro variable reference?

e.g. &varx where var is the macro variable

What if you want to have a period right after the macro variable

e.g. &libref.dataset

Answer 20

Add a period after the macro variable

&var.x

Add 2 periods

&libref..dataset

Question 21

What do you use when you want to assign a macro variable within a DATA step?

Answer 21

CALL SYMPUT(macroname, value)

macroname and value can be:

a literal, enclosed in quotation marks

a DATA step variable

a DATA step expression

Question 22

How do you convert from character to numeric? From numeric to character?

Answer 22

Character to numeric:

INPUT(“text”, informat)

Numeric to character:

PUT(number, format)

Question 23

How is CALL SYMPUTX different from CALL SYMPUT?

Answer 23

CALL SYMPUTX removes leading and trailing blanks from both the macro variable name and its value

Question 24

How many &s do you need in front of a macro variable name when its value matches the name of a second macro variable that you want to resolve?

e.g.

%let a = apple

%let apple = yummy

How do you get yummy by referencing a

Answer 24

&&&

This is the forward re-scan rule.

Two ampersands get resolved to &, so need a third ampersand

(See pg. 347)

&a and &&a resolve to apple

&&&a first resolves to &apple, which on re-scan resolves to yummy

Question 25

%let teach1 = Mr. Rogers

%let teach2 = Ms. Clare

%let teach3 = Mr. Simmons

%let num = 3

How do you reference teach3 using the num macro variable?

Answer 25

&&teach&3

On first pass, this will resolve to &teach3, which then resolves to Mr. Simmons

Question 26

How do you obtain the value of a macro variable during a DATA step execution?

Answer 26

Use SYMGET(macroname)

use quotation marks for a macro variable name

can also be a DATA step variable name or expression (no quotation marks)

Question 27

Syntax to create a single macro variable during a PROC SQL Step Execution

Answer 27

macro variable can only store one value, so need a summary function

proc sql noprint;

select sum(column1)

into :macroname

from table1;

Question 28

Syntax to create multiple macro variables in PROC SQL step

Answer 28

proc sql;

select column1, column2

into :macro1 - :macro-n,

:anothermacro1 - :anothermacro-n

from table1;

Question 29

Syntax to create a macro variable that holds multiple values in a PROC SQL step

Answer 29

proc sql;

select column1

into :macroname

separated by‘delimiter’

from table1;

Question 30

What is the difference in these two codes:

proc sql;

create view subcrsid as

select student_name, student_company, paid

from sasuser.all

where course_code=”&crsid”;

quit;

proc sql;

create view subcrsid as

select student_name, student_company, paid

from sasuser.all

where course_code=symget(‘crsid’);

quit;

Answer 30

The macro variable referenced by &crsid is resolved during the creation of the view, so it has a constant value whenever the view is used. e.g. if at creation crsid=003, it keeps this value.

Using SYMGET allows the view to look up the macro variable value when the view is used