BAS 150 Lesson 8 Lecture

• Explain how a SAS Macro works
• Create a SAS Macro and SAS Macro Variable
• Incorporate a SAS Macro into an existing program
This Lesson’s Learning Objectives

SAS Macros (1 of 2)
 Most Important Concept to remember:
“You are writing a program that writes a program!”
 Macros help you in many ways:
o They allow you to write one section of code and use it over and over
again.
o You can make one small change in your code and have SAS make
that change throughout your program.
o You can make your program similar to an algorithm, letting SAS
decide what to do with the actual data.
The macro is a tool for simplifying and automating repetitive tasks

SAS Macros (2 of 2)
Macros vs. Macro Variables:
• SAS Macro
o Often contains a Macro variable
o Larger piece of program
o Can contain complex logic
• SAS Macro Variable
o Standard data variable – does not belong to a data set
o Only a single value, typically a character value
o Value of a Macro variable could be a name, numerical or text

 The macro language is the syntax you use to create and
use macros
 A macro variable is an efficient way of replacing text
strings in SAS code
o &name
 A macro is a predefined routine you can use in a SAS
program
o %name
What are macros?

 %LET is a macro statement that creates a macro variable and
assigns it a value
 Useful for simplifying code and automating reports
 Macro variable can be used anywhere in SAS code, such as:
o Titles/Footnotes
o IF/WHERE statements
o Filenames
o Almost anywhere you have text capabilities
%LET (1 of 3)

%LET macro-variable = <value>;
 macro-variable : name of new macro variable
 value : character string or text expression that the macro
variable will represent
 Resolve the macro variable later in your code with an
ampersand: &macro-variable
%LET (2 of 3)

 Report run every day for a product you choose
 Each time you have to change the TITLE statement
and the date parameters in the WHERE statement
%LET (3 of 3)

 Reference a macro variable with an ampersand preceding its name
 If within a literal string (such as a title statement), enclose the string in
double quotation marks
o Macro variable references in single quotation marks will not resolve
Referencing Macro Variables (1 of 7)

 Macro variable references can be placed next to leading or
trailing text
 Output = “Sales as of Wednesday October 5 2016”
%LET product_name = ‘Orange';
%LET type_name = ‘Navel';
proc print data = store1011.produce;
where product = &product_name and type = &type_name ;
TITLE "Sales as of &SYSDAY &SYSDATE"; run;

 The period delimiter will resolve with the macro variable reference
 You may need a second period as part of the original text
 HDD Report &Year..pdf resolves to HDD Report 2012.pdf
o The first period is the delimiter for the macro reference, and the second
is part of the text

 Macro variable references can also be placed
next to each other

 Use %put to see the resolved macro reference
in your log
o Can be useful for quickly de-bugging macro
references
Resolving Macro Variables (5 of 7)

 Use the symbolgen option to display the resolution of macro
variable references in the log at the time they are executed
o Can also be useful for de-bugging

 Macro variables are constant text strings
 Even if it looks like an equation, it will be
treated like text

 Use the %eval function to evaluate the
expression using integer arithmetic
%EVAL and %SYSEVALF (1 of 3)

 %eval cannot be used with floating-point
numbers (numbers with a decimal point)

 Use the %sysevalf function for floating-point
arithmetic

 SAS has built in macro
variables called automatic
macro variables
o They are created at the
beginning of every SAS
session
o Use %put
_automatic_; to see the
list in the log
Automatic Macro Variables (1 of 2)

 Some potentially useful automatic macro
variables:
o SYSDATE
o SYSDATE9
o SYSDAY
o SYSTIME
o SYSUSERID
Automatic Macro Variables (2 of 2)

 How do you turn today’s date into a macro variable?
 Option 1: Use the SYSDATE or SYSDATE9 automatic
variables
o Problem – SYSDATE and SYSDATE9 are not dates, but
text strings. What if you don’t like that format?
 Option 2: Use CALL SYMPUTX
CALL SYMPUTX (1 of 8)

 CALL SYMPUT and CALL SYMPUTX assign
a value to a macro variable (similar to %LET)
 Unlike %LET, the value can be based on a
calculation, algorithm or dataset variable

 Below is an example of CALL SYMPUTX
 The end result is macro variable that contains
today’s date with no special characters
o Useful for adding a date to filenames

 DATA _NULL_
o Allows you to execute a DATA step without
creating a new dataset

 TODAY()
o Computes the current date
o Example: March 26, 2013

 PUT(today(), MMDDYY10.)
o Converts today’s date into a character string
o The string will have the appearance of the
MMDDYY10. date format
o Example: 03/26/2013

 COMPRESS(put(today(), mmddyy10.), ‘/’)
o Removes the forward slashes from the text string
o Example: 03262013

 CALL SYMPUTX(‘DATE’,
compress(put(today(), mmddyy10.), ‘/’))
o Assigns this value to a macro variable called
DATE
o Similar to %LET date = 03262013;

 Example: Have the DATA step store the SYSUSERID
and SYSDATE to keep record of who last modified the
dataset
SYMGET Function (1 of 2)

 The SYMGET function, by default, stores the
new variables as character variables with a
length of 200
SYMGET Function (2 of 2)

 Anytime you find yourself repeating tasks or programs, you
might want to consider creating a macro
 Macros are simply a group of SAS statements with a name
 Instead of re-typing the statements, you use the macro
name to invoke the code
 The invoked macro will write the code to your program
o Think of it as an advanced version of find/replace
Macro Programs (1 of 2)

%MACRO macro-name <(parameters)>;
macro-text
%MEND macro-name;
 macro-name : name of new macro program
 parameters : local macro variables, whose values you specify
when you invoke the macro
 Resolve the macro variable later in your code with a percent sign:
%macro-name <(parameters)>
Macro Programs (2 of 2)

 Use parameters to increase the flexibility of your macro
 Similar to %LET
Parameters

 Macro parameters are local macro variables
o They are defined in macro code
o They can only be used within the macro that defines them
 Other macro variables are global macro variables
o They are defined in open code (non-macro code)
o They can be used anywhere in open code and in macro code
o Examples include automatic macro variables, variables created with %LET
Best practice: Do not create a local and global macro variable with the same name
Global vs Local

 %IF, %THEN, %ELSE is similar to IF, THEN, ELSE,
but they are not the exactly same
o IF, THEN, ELSE conditionally executes SAS
statements in the DATA step
o %IF, %THEN, %ELSE conditionally generates text in a
macro
%IF, %THEN, %ELSE (1 of 2)

• Explain how a SAS Macro works
• Create a SAS Macro and SAS Macro Variable
• Incorporate a SAS Macro into an existing program
Summary - Learning Objectives

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BAS 150 Lesson 8 Lecture

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BAS 150 Lesson 8 Lecture