BAS 150Lesson 8: SAS Macros

• 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 variableo Larger piece of programo Can contain complex logic

• SAS Macro Variable

o Standard data variable – does not belong to a data seto Only a single value, typically a character valueo 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”

Referencing Macro Variables (2 of 7)

%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

Referencing Macro Variables (3 of 7)

Macro variable references can also be placed

next to each other

Dataset name HDD&Month&Year will resolve

to HDDApril2012

Referencing Macro Variables (4 of 7)

Use %put to see the resolved macro reference

in your log

oCan 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

Resolving Macro Variables (6 of 7)

Macro variables are constant text strings

Even if it looks like an equation, it will be

treated like text

Resolving Macro Variables (7 of 7)

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)

%EVAL and %SYSEVALF (2 of 3)

Use the %sysevalf function for floating-point

arithmetic

%EVAL and %SYSEVALF (3 of 3)

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

CALL SYMPUTX (2 of 8)

Below is an example of CALL SYMPUTX

The end result is macro variable that contains

today’s date with no special characters

oUseful for adding a date to filenames

CALL SYMPUTX (3 of 8)

DATA _NULL_

o Allows you to execute a DATA step without

creating a new dataset

CALL SYMPUTX (4 of 8)

TODAY()

oComputes the current date

o Example: March 26, 2013

CALL SYMPUTX (5 of 8)

PUT(today(), MMDDYY10.)

oConverts today’s date into a character string

o The string will have the appearance of the

MMDDYY10. date format

o Example: 03/26/2013

CALL SYMPUTX (6 of 8)

COMPRESS(put(today(), mmddyy10.), ‘/’)

oRemoves the forward slashes from the text string

o Example: 03262013

CALL SYMPUTX (7 of 8)

CALL SYMPUTX(‘DATE’,

compress(put(today(), mmddyy10.), ‘/’))

o Assigns this value to a macro variable called

DATE

o Similar to %LET date = 03262013;

CALL SYMPUTX (8 of 8)

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)

Writing a Macro

Invoking a macro

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)

%IF, %THEN, %ELSE (2 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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