I OWA S TATE U NIVERSITY Department of Animal Science Writing Flexible Codes with the SAS Macro...

IOWA STATE UNIVERSITYDepartment of Animal Science

Writing Flexible Codes with the SAS Macro Facility

(Chapter in the 7 Little SAS Book)

Animal Science 500

Lecture No. 7

September 21, 2010


SAS Macro Development

u SAS Macros used to be utilized by “more advanced” SAS Users

u Today SAS Macros are being used by more and more peoplen Including beginnersn Using existing Macrosn Developing your own Macros


General Macro Knowledge

u Macros typically take longer to write and debug than a normal SAS program that you might only use a few times

u After Macros are developed n Make developing maintaining a “production” program that is

used a great deal easier1. You can have SAS make a change in one part of your program and

have SAS “echo” that throughout the rest of the program

2. Allows you to write a piece of SAS code and reuse it several times either the same day or days later


The Macro Processor

u Compiling “submitting your code” your SAS program is different than when submitting a SAS Macron Your standard SAS code is submitted and immediately

executed n Macros have an additional step

l SAS passes the Macro statement to the macro processor which “resolves” your macros that generates standard SAS code

l Called meta programming because you write a program that writes a program


Macros and macro variables

u SAS macro code has two parts1. Macros

2. Macro variables

u Name of the Macro is prefixed with a %

u Name of the Macro variables is prefixed with an &n Is like your variable in a data set except it is not associated

with a data set and it is always a character variablel Can be

A variable name A numeral Any text you want substituted into your program


Macros and macro variables

u Macro is a larger piece of program that may contain complex logic n Datan Proc Statements

u Macro Statementsn %Don %Endn %IF-n %Then/n %Else


Macros

u Macro variable can have different “scopes”n Local – defined within the macron Global – macro code that is outside of the macro

- Use global macro variable anywhere in your program

- A local macro variable can only be used inside the macro

- Cannot have a global and local macro variable with the same name.


Invoking or Turning on the Macro Processor

u Must turn on the MACRO system option in order to use itn Macro is usually on by defaultn May be turned off – especially true on mainframe computer

systems (usually seen in larger businesses, ISU has what some would consider a mainframe but not used by general studentsl SAS runs faster if it does not have to check and see if there are

macros are presentl If MACROS are turned off that means SAS does not have to check

for them


Invoking or Turning on the Macro Processor

u To check and see whether the MACRO option is on use the following SAS code:

PROC OPTIONS OPTION = MACRO;

RUN;

QUIT;

u Examine the SAS logn If you see

1. the option MACRO then the macro processor is turned on

2. NOMACRO the macro is turned off and you need to specify the MACRO option at invocation or in a configuration file

* Specifiying this type of option is system dependent - check your SAS Help and Documentation for your operating system


Substituting Text with Macro Variables

u Suppose you have a SAS program that you run once a week

u Each time you run the program you have to edit the program so it will select data for the correct range of dates and print the correct dates in the titlen Time consumingn Errors frequently happen and then are correct (even

time consuming) or you send a report that has errors (bad image)



u Can use a MACRO variable to insert the correct date;

u Using the macros in this manner allows a much less experience person to generate the report –n The person does not have to know SAS code because

the changes are made automatically



u When SAS encounters the name of a macro variable, the macro processor replaces the name with the value of that macro variable.

u Simplest way to do this:n Use the Macro called %Let

n General form %Let macro-variable-name = valuen The macro-variable-name must follow normal SAS rules

l 32 characters or less l Start with a letter or _l Contain only letters, numerals, or underscores.


Substituting Text with Macro Variablesn General form %Let macro-variable-name = valuen The macro-variable-name must follow normal SAS rules

l 32 characters or less l Start with a letter or _l Contain only letters, numerals, or underscores.

n value is the text that is substituted for the macro variable name can be longer than you will ever need 64,000 characters long

u The following statements each create a macro variablen % Let iterations = 10;n % Let country = New Zealand;


Substituting Text with Macro Variablesu The following statements each create a macro variable

n %Let iterations = 10;n %Let country = New Zealand;

** Notice that unlike ordinary assignment statement like infile, value does not need quotation marks (‘ ’ or “ ” )

** Except for the blanks at the beginning and end, which are trimmed, everything between the equals sign and the semicolon becomes part of the value for that macro variable


Using a Macro Variableu To use a macro variable you just add the & sign (ampersand) and

stick the macro variable name wherever you want its value to be substituted.

u The macro processor doesn’t look for macros inside single quotation marks to get around this you must use double quotations “ ”.

u Do i = 1 to &iterations;

u TITLE “Addresses in &country”;

u After being resolve by the macro processor, these statements would result in the following:

u Do i = 1 to 10; (the 10 came from code on previous slide)

u Title “Addresses in New Zealand”;


Adding Parameters to MACROS

u Prologn Macros allow you to use the same set of statements

over and overn Parameters are macro variables whose value you set

when you invoke a macro


Example

u A macro named %QUARTERLYREPORT might start liken %MACRO quarterlyreport (quarter= , salesrep = );n This macro has two parameters &QUARTER and

&SALESREP.n You invoke the macro with the following statementn %quarterlyreport (quarter=3, salesrep=smith)


Example

u Suppose the grower often needs a report showing sales to an individual customer and then sort the results. The data contain the customer ID, date of sale, variety of flower, and quantity.


Data

-------+--------1--------+--------2--------+--------3

240W 02-07-2000 GINGER 120

356W 02-08-2000 HELICONIA 60

356W 02-08-2000 ANTHURIUM 300

188R 02-11-2000 GINGER 24

188R 02-11-2000 ANTHURIUM 24

240W 02-12-2000 PROTEA 180

356W 02-12-2000 GINGER 240


Program%LET flowertype = Ginger;

* Read all the flower sales data and subset with a macro variable;DATA flowersales;

INFILE ‘c:\mydocuments\sales\sales.dat’;INPUT CustomerID $4 @6 Saledate MMDDYY10. @17

Variety $9. Quantity;IF Variety = “&flowertype”;

Run;Quit;* Invoke a macro to Print the report using a macro variablePROC PRINT DATA = flowersales;

FORMAT Saledate WORDDATE18.;TITLE “Sales of &flowertype”;Run;Quit;


Output from Macro ExampleSales of Ginger

Customer

Obs ID SaleDate Variety Quantity

1 240W February 7, 2008 Ginger 120

2 188R February 11, 2008 Ginger 24



Program

* Macro with parameters%MACRO select (customer=, sortvar=);

PROC SORT DATA = flowersales OUT = salesout;BY &sortvar;WHERE CustomerID = “&customer”;

PROC PRINT DATA = salesout;FORMAT SaleDate WORDDATE18.;TITLE “Orders for Customer Number

&customer”;%MEND select;


Output looks like this:Orders for Customer Number 356W 1

Customer

OBS ID SalesDate Variety Quantity

1 356W February 8, 2000 Anthurium 300


3 356W February 8, 2000 Heliconia 60

Orders for Customer Number 240W 2

Customer

OBS ID SalesDate Variety Quantity


2 240W February 12, 2000 Protea 180


Creating Modular Code with Macros

u If you are writing the same or similar SAS statements over and over consider using a Macro.n You can package a piece of bug free code and use it

repeatedly within the same SAS program or in many programs

u %Macro and %Mend can be thought of as a sandwichn You can put anything you want


Creating Modular Code with Macros

u %Macro and %Mend can be thought of as a sandwichn You can put anything you wantn General form is:

%MACRO macro-name; (tells SAS it’s the beginning of a Macro)

macro-text

%MEND macro-name; (tells SAS it’s the end of a Macro)

Macro-name is a name you can make up

up to 32 characters

start with a letter or _

contain only letters, numerals, and underscores


Creating Modular Code with Macrosn General form is:

%MEND macro-name; n The macro-name in the MEND statement is

optional.n Macros will be easier to debug or remove errors if the macro-name is included in the MEND statementn Easier to match MACRO and MEND statements

makes the sandwich complete


Macros

u Macros can be stored in a central location called an autocall locationn Can be used multiple times in different programs by a

single programmern Can be used by multiple programers if they have access

to a centrally stored autocall location as long as they have access or permission

n Easy way to store macros that might be useful multiple times by a single or multiple users


Macros

u Macros can have multiple parameters n Same report but with a different set of datan Example

l %Macro macro-name (parameter-1= , parameter-2 , parameter-n= );

Macro-text;

%MEND macro-name;

Example: A macro named %QUATERLYREPORT might start like this;

%Macro quarterlyreport (quarter= , salesrep= );

Could invoke Macro by the following statement;

%quarterlyreport (quarter=3,salesrep=Smith);


Macros

u Likely will not use macros a great deal with one exception

u A macro called PDMIXn Separates means from a Proc Mixed analysis with a

user defined separation techniquel Duncans, Tukeys, etc.

n Assigns letter names to separated means of one or more class variable defined in a Proc Mixed analysis


PDMIX macro

PURPOSE: This macro takes two data sets from Proc MIXED (Version 8), created by the DIFFS option on the LSMEANS statement. If an ADJUST= option is used, the pdiffs from this are used, not the unadjusted defaults. The pdiffs are converted to groups, labeled by numbers, and this is merged onto the lsmeans data set. The numbers are converted to letters, and for cases where more than 26 letters are needed, sections of letters are coded. For example, 3 means might have the letters A, (2)A, and (3)A. These 3 means are all different, because although all have the letter A, each A belongs to a different section, identified by (#).


Example use of PDMIX Macro

Example of use. Assume the file pdmix800.sas, containing the macro code, is on the a: drive. Then the code below will run MIXED, and run pdmix800 on the lsmeans. MIXED is told not to print the means and pdiffs, using the ODS exclude statement, as pdmix800 does the printing in the more desirable format. Also shown are two optional parameters.


Example use of PDMIX Macro

Proc Mixed; class block a b; model y = a b a*b; random block; lsmeans a b a*b/pdiff; ods output diffs=ppp lsmeans=mmm; ods listing exclude diffs lsmeans; run; %include 'a:pdmix800.sas'; %pdmix800(ppp,mmm,alpha=.01,sort=yes);

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