adv. sas(macro)

8/20/2019 Adv. SAS(Macro)

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SAS Training


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Macro

• Used to reduce the amount of code entered to perform common tasks

• Used for tasks that are repeated in number of programs or number of different places within aprogram.

• It is used to automatically generate

– SAS statements and commands

– write messages to the SAS log

– Accept input

– Create and change the values of macro variables

• Macro facility has two components

1. Macro Processor – A part of SAS system does the Macro processing

2. Macro Language – Syntax that communicates to Macro Processor


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Two delimiters trigger macro processor activity:

• &name - macro variable.

– Replacing Text Strings Using Macro Variables

– The form &name is called a macro variable reference.

• %name - refers to a macro

– Generating SAS Code Using Macros

– The form %name is called a macro call

• The text substitution produced by the macro processor is completed before the program text iscompiled and executed

• Macro language elements can only trigger text subs t i tut ion and are not present during programor command execution


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Defining Macro

• A SAS program can contain any number of macros

• can invoke a macro any number of times in a single program

• Should always start with a %macro statement and end with a %mend statement

Syntax

%MACRO macro-name;

macro definition

%MEND macro-name;

where,

• macro-name is the name of the macro. Each macro should have a distinct name, which is subjectto the standard SAS naming conventions.

• Macro definition can be any valid SAS step


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Example

%MACRO print;

PROC PRINT DATA = ipl.bowlers;

RUN;

%MEND;

• Defining a macro called print for printing the data set bowlers.


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Calling a Macro

• %name - refers to a macro

• The form %name is called a macro call.

Syntax

%macro-name;

where,

• macro-name is the name of the macro, which is to be called.

Example :- %print;

• %print will call the previously defined macro and print the dataset candy.


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Example

%print;

Obs name category

1 Bhatia BW

2 Vettori BW

3 Maharoof BW

4 Geeves BW

5 McGrath BW


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Passing Information into a Macro Using Parameters

• Macro parameters are local macro variables whose values are specified while invoking themacro

• Macro variables defined in parentheses in %MACRO statement

• Enable to pass information into a macro

• Two types

• Positional Parameters

• Keyword Parameters

Syntax

%macro macro-name(var1 ,var2,….varn );

macro definition

%mend macro-name;

where,

• var1, var2 - macro variables – stores the values of the parameters passed.Refer to a macrovariable as &name in the macro definition. The form &name is called a macro variable reference.


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Keyword Parameters

• names one or more macro parameters followed by equal signs

• can specify default values after the equal signs or specify the macro variable name followed byan equal sign and the value in the macro invocation

Syntax

%macro macro-name (var1 = [val1] ,var2 = ,….varn = );

macro definition%mend macro-name;

where,

• var1, var2 - macro parameters for holding the values passed.• val1 is the default value to be stored in the parameter, to be used if no value is passed


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Example

%macro players(match=1, innings=);

proc print data=ipl.players noobs;

var name type;where match=&match and innings=&innings;

title “The names of the players for match &match and innings &innings”;

run;

%mend players;

%players(innings=1);

%players(innings=1,match=2);

The names of the players for match 1 and innings 1

name category

Gambhir BT

Dhawan BT

The names of the players for match 2 and innings 1

name category

Karthik BT


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Positional Parameters

• Names one or more macro parameters whose values will be specified while macro invocation

• Specify the values in the same order its defined in the macro definition

• If no value is specified while invocation, null value will be taken

Syntax

%macro macro-name (var1,var2 ,….varn );macro definition

%mend macro-name;

where,

• var1, var2 - macro parameters for holding the values passed.


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Example

%macro players(plname,cat);

proc print data=ipl.players noobs;

where name=&plname and category=&cat;tilte "&plname is a &cat";

run;

%mend players;

%players ("Bhatia“,"BW");

name category

Bhatia BW


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Macro Variables

• Are tools that enable you to dynamically modify the text in a SAS program through symbolicsubstitution

• Can assign large or small amounts of text to macro variables

• Maximum length of 65,534 characters

• Are independent of SAS data set variables

• Use the variable by referencing it with an ampersand preceding its name (&variable-name),anywhere in a SAS program

• Macro variable references that are enclosed in single quotation marks are not resolved

• Classified into two based on the scope of the variable

• Global Macro Variable

• Local Macro Variable


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• Can create a macro variable by using a let statement

• Using a let statement inside a macro definition creates a local macro variable

• Using a let statement outside a macro definition creates a global macro variable

Syntax

%let = ;

where,

• is a name for the macro variable, satisfying SAS rules

• is the value to be assigned to the macro variable

Example:

%let playername = Tendulkar ;

%let sum = (100 + 400) ;


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Global Macro Variables

• Exist till the duration of the SAS session

• Can be used within or outside a Macro

• Created during anytime of the SAS session

• Can assign a value using a let statement later

Syntax

%gobal ;

where,


Example: %global playername;


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Local Macro Variables

• Can be declared within the sas macro using let statement or using the keyword local

• Exists till the execution of that macro in which the variable is created.

• It can be accessed/changed within the creation of macro.

Syntax

%local ;

where,


Example

%local player;


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Defining Arithmetic and Logical Expressions

• can use arithmetic and logical expressions in specific macro functions and statements

• Macro Language Elements that Evaluate Arithmetic and Logical Expressions• %DOmacro-variable=expression %TO expression;

• %DO %UNTIL(expression);

• %DO %WHILE(expression);

• %EVAL (expression);

• %IF expression %THEN statement ;

• %SCAN(argument,expression,)• %SUBSTR(argument,expression)

• %SYSEVALF(expression,conversion-type)


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Example

%let a=%eval(1+2);

%let b=%eval(10*3);

%let a=%sysevalf(10.0*3.0);%let b=%sysevalf(10.5+20.8);

%let address=123 maple avenue;

%let frstword=%scan(&address,1);

%let lincoln=Four score and seven;%let secondwd=%substr(&lincoln,6,5);


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Example

%macro whatstep(info=,mydata=);

%if &info=print %then

%do;proc print data=&mydata;

run;

%end;

%else %if &info=report %then

%do;

proc report data=&mydata nowd;

column name category;title "DLF IPL 2008";

run;

%end;

%mend whatstep;

%whatstep (info=report, mydata=player)


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SYMPUT Routine

• Assigns a value produced in a DATA step to a macro variable

Syntax

CALL SYMPUT(macro-variable, value);

where,

• macro-variable can be a character string that is a SAS name, enclosed in quotation marks orname of a character variable whose values are SAS names

• data team1;

• input position : $8. player : $12.;

• call symput(position,player);

• datalines;

• shortstp Ann• pitcher Tom

• frstbase Bill

• ;


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Example

%let sr_cit = no;

data senior;

set census;if age > 65 then

do;

call symput ("sr_cit", yes);

output;

end;

run;

data team1;

input position : $8. player : $12.;

call symput(position,player);

datalines;

shortstp Ann

pitcher Tomfrstbase Bill

;

run;


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Automatic Macro Variable

• Macro processor creates automatic macro variables that supply information related to the SASsession when SAS is invoked

• Use %PUT _AUTOMATIC_ to view all available automatic macro variables

Example

SYSDAY

SYSDATE

SYSMACRONAME


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User-Defined Macro Variable

• Macro variables created by the user

• Use %PUT _USER_ to view all available user-defined macro variables

Example

%let city = Bangalore;

%let player = Tendulkar;

%let sum = %eval(100 + 400);

• City, player and sum are macro variables


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Displaying Macro Variable Values

• Use the %PUT statement to display macro variable values

• Values will be displayed in log window

Syntax

%put &macro-variable;

Example

%put &player;

%put ∑


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Including external macros

• Macros can be stored in external file can be used again

%include “c:\files\name.sas”;

%players

%players (print=0)

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