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SAS: Macros

SAS: Macros. Computing for Research I Spring 2013 January 29, 2013 . What can MACROS do for you?. Avoid repetitious SAS code Create generalizable and flexible SAS code Pass information from one part of a SAS job to another Conditionally execute data steps and PROCs

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SAS: Macros

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  1. SAS: Macros Computing for Research I Spring 2013 January 29, 2013 

  2. What can MACROS do for you? • Avoid repetitious SAS code • Create generalizable and flexible SAS code • Pass information from one part of a SAS job to another • Conditionally execute data steps and PROCs • Dynamically create code at execution time

  3. What are Macros and why do we need /use them? • A macro is a way to automate a task that you perform repeatedly or on a regular basis. • It is a series of commands and actions that can be stored and run whenever you need to perform the task. • Can you think of situations where you may want or have used a macro?

  4. SAS PROC statements • In essence all of the PROC statements in SAS are macros. They have been written, validated and incorporated into the system so that they can be used repeatedly when called to perform specific tasks.

  5. Example: PROC MEANS • Provides data summarization tools to compute descriptive statistics for variables across all observations and within groups of observations. • Calculates descriptive statistics based on moments • Estimates quantiles, including the median • Calculates confidence limits for the mean • Indentifies extreme values • Performs a t test

  6. What is the macro facility? • A tool for extending and customizing SAS and for reducing the amount of text you must enter to do common tasks. • Enables you to assign a name to character strings or groups of SAS programming statements.

  7. Components of macro facility: • The macro processor • The portion of SAS that does the work • The macro language • The syntax that you use to communicate with the macro processor

  8. Macro Processor Macro statements Standard SAS statements Macro processor

  9. How do we “trigger” the SAS macro processor? • &name • Refers to a macro variable • The form &name is called a macro variable reference. • %name • Refers to a macro • The form %name is called a macro call.

  10. What we will cover: • Macro Variables and Using them for specific functions • SAS defined macro variables • How do we use these in conjunction with SAS code? • Creating SAS Code Using Macros • Defining SAS macros • SYNTEX for SAS macros • Calling SAS macros • Applications • Examples

  11. Macro Variables • An efficient way of replacing text strings in SAS code. • Can be defined within a macro definition or within a statement that is outside a macro definition, referred to as OPEN code. • Are independent of SAS data set variables.

  12. Macro Variables defined by SAS • When you invoke SAS, the macro processor creates automatic macro variables that supply information related to the SAS session.

  13. Macro Variables defined by SAS Some automatic SAS macro variables SYSCMD LAST NON-SAS COMMAND ENTERED SYSDATE CURRENT DATE IN DATE6. OR DATE7. FORMAT SYSDAY CURRENT DAY OF THE WEEK SYSDEVIC CURRENT GRAPHICS DEVICE SYSDSN LAST SAS DATASET BUILT SYSINDEX NUMBER OF MACROS STARTED IN JOB SYSINFO SYSTEM INFORMATION GIVEN BY SOME PROCS SYSPROD INDICATES WHETHER A SAS PRODUCT IS LICENSED SYSSCP OPERATING SYSTEM WHERE SAS IS RUNNING SYSTIME STARTING TIME OF JOB SYSVER SAS VERSION

  14. Macro Variables defined by SAS • To use an automatic macro variable, reference it with an ampersand followed by the macro variable name. • Example: SYSDATE and SYSDAY • SYSDATE contains a SAS date value in the DATE7. format, which displays a two-digit date, the first three letters of the month name, and a two-digit year. • SYSDAY contains a SAS day value

  15. Macro Variables defined by Users • Scope – Global vs Local • %GLOBAL – used to define a global macro variable • Naming conventions • Must start with a letter or _ • Can be followed by letters or digits • Cannot be a reserved word (HANDOUT 1)

  16. Macro Statements • Begin with a % and a macro keyword and end with a semicolon (;) • Assign values, substitute values, and change macro variables • Can branch or generate SAS statements conditionally

  17. Macro Variables defined by Users %LET How do we use this? %LET CITY=CHARLESTON; TITLE “Demographics Data for &CITY”;

  18. Macro Variables defined by Users %LET CITY=CHARLESTON; TITLE “Demographics Data for &CITY”; Notes: • Once a macro variable is defined, you must precede the name of the macro variable with an ampersand (&) each time it is used. • If a macro variable appears within a quoted string, double quotes must be used to ensure that the macro variable ‘resolves’ to its assigned value.

  19. Macro Program Statements • %DO • %GLOBAL • %LOCAL • %MACRO and %MEND

  20. Macro Functions • Processes one or more arguments and produces a result. • Can use all macro functions in both macro definitions and open code. • Examples: (%EVAL, %LENGTH, %UPCASE, %PUT)

  21. Using and Displaying Macro Variables %LET A=1+2; %LET B=10*3; %LET EVAL_A=%EVAL(&A); %LET EVAL_B=%EVAL(&B); %PUT &A IS &EVAL_A; %PUT &B IS &EVAL_B; • SUBMIT TO GET:

  22. Using and Displaying Macro Variables %LET A=HAPPY; %LET B=BIRTHDAY; %PUT THE LENGTH OF &A IS %LENGTH(&A).; %PUT THE LENGTH OF &B IS %LENGTH(&B).; • SUBMIT TO GET:

  23. Using and Displaying Macro Variables %LET A=2; %LET B=5; %LET OPERATOR=+; %PUT THE RESULT OF &A &OPERATOR &B IS %EVAL(&A &OPERATOR &B).; • SUBMIT TO GET:

  24. Assigning SAS Statements %LET DESSTAT=%STR(PROC MEANS;RUN;); … &DESTAT; • WHAT HAPPENS WHEN THIS IS RUN?

  25. Notes to consider about macro variables: • Double quotation marks, i.e. “ “ vs ‘ ‘ • Variable length • Special characters • Condition operations • Complex tasks

  26. Generating SAS Code Using Macros • Macro Processing • Need to define what the macro function will be • Process that SAS uses to program macro elements • Macro Programs • Offers more programming flexibility than macro variables in that you can pass information to parts of the macro program via macro parameters

  27. SAS Macros • Can include: • Constants such as literals, variables, names, and statements • Assignments to macro variables • Macro programming statements • Macro language functions • Invocations of other functions • Nested macro definitions • LOGIC to conditionally generate SAS code

  28. Defining and Calling Macros %MACRO macro-name; macro text %MEND macro-name;

  29. Example: %MACRO FUNMAC (DATASET, VAR1, VAR2); DATA RTEMP; SET &DATASET; RUN; PROC MEANS; VAR &VAR1 &VAR2; RUN; %MEND FUNMAC; %FUNMAC (RDATA, AGE, WEIGHT);

  30. Application in SAS code: • Vitals data over time • Summary statistics using PROC TABULATE • Categorical variables • Continuous variables

  31. Vitals Data over time: DATA FORM05; SET ALISAH.FORM05; SUBJECTID=ZSUBJECTID; MAX_CVPRESS=F05Q02; WEIGHT=F05Q06; MAX_SBP=F05Q07; MAX_DBP=F05Q09; MAX_HR=F05Q13; KEEP SUBJECTID ZVISITID MAX_CVPRESS WEIGHT MAX_SBP MAX_ DBP MAX_HR; RUN; PROC SORTDATA=FORM05 OUT=FORM05T;BY SUBJECTID ZVISITID; RUN;

  32. Vitals Data over time: *MACRO TO CREATE MULTIPLE DATA SETS-ONE FOR EACH DAY OF VITALS; %MACRO VITALS(DAY, VISIT, DATASET); DATA &DAY._VITAL (KEEP=SUBJECTID MAX_CVPRESS& WEIGHT&DAY MAX_SBP&DAY MAX_DBP&DAY MAX_HR&DAY); SET &DATASET; IF ZVISITID=&VISIT; MAX_CVPRESS&DAY=MAX_CVPRESS; WEIGHT&DAY=WEIGHT; MAX_SBP&DAY=MAX_SBP; MAX_DBP&DAY=MAX_DBP; MAX_HR&DAY=MAX_HR;

  33. Vitals Data over time: LABEL MAX_CVPRESS&DAY="MAXIMUM CENTRAL VENOUS PRESSURE&DAY."; LABEL WEIGHT&DAY="WEIGHT&DAY."; LABEL MAX_SBP&DAY="MAX SYSTOLIC BLOOD PRESSURE&DAY."; LABEL MAX_DBP&DAY="MAX DIASTOLIC BLOOD PRESSURE&DAY."; LABEL MAX_HR&DAY="MAX HEART RATE&DAY."; RUN; PROC SORT DATA=&DAY._VITAL; BY SUBJECTID; RUN; %MEND VITALS;

  34. Vitals Data over time: *CALLING MACRO TO CREATE THE DATA SETS FOR VITALS; %VITALS (BASE, 1, FORM05); %VITALS (D1, 2 , FORM05); %VITALS (D2, 3 , FORM05); %VITALS (D3, 4 , FORM05); %VITALS (D4, 5 , FORM05); %VITALS (D5, 6 , FORM05); %VITALS (D6, 7 , FORM05); %VITALS (D7, 8 , FORM05);

  35. Vitals Data over time: /*MACRO TO CREATE NEW VARIABLES TO BE USED IN MERGED DATA SET TO CALCULATE DIFFERENCE EACH DAY FROM BASELINE*/ %MACRO CHANGES(NEWVAR, VAR1, VAR2, VITAL, DAY); IF &VAR1 NE . AND &VAR2 NE . THEN %DO; &NEWVAR=&VAR1-&VAR2; %END; LABEL &NEWVAR="CHANGE IN &VITAL. FROM BASELINE TO &DAY."; %MEND CHANGES;

  36. PROC TABULATE for Categorical Variables: *CATEGORICAL MACRO BY TREATMENT GROUP; %MACRO CATEGORY( INDATA, MYVAR, MYTITLE) ; DATA INDATA;SET &INDATA; RUN; PROC TABULATE DATA=INDATA MISSING FORMAT=7.0 STYLE=[FONT_SIZE=1.5]; CLASS &MYVAR ZTREATMENTCODE /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE] ; TABLE ALL="ALL SUBJECTS" &MYVAR=" ", (ZTREATMENTCODE ALL="ALL GROUPS")*(N PCTN<&myvar ALL>*F=PCTFMT7.) /BOX=[LABEL="&MYTITLE“ STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]] MISSTEXT="0" PRINTMISS; LABEL ZTREATMENTCODE="TREATMENT GROUP"; KEYLABEL N="N" PCTN="PERCENT"; CLASSLEV &MYVAR ZTREATMENTCODE /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; KEYWORD ALL N PCTN /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; RUN; %MEND;

  37. PROC TABULATE for Continuous Variables: %MACRO CONTINUOUS (INDATA, MYVAR, MYTITLE); PROC TABULATE DATA=&INDATA FORMAT=10.0 STYLE=[FONT_SIZE=1.5]; VAR &MYVAR/STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; CLASS ZTREATMENTCODE /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; TABLE ALL="ALL RANDOMIZED" &MYVAR*(N="TOTAL_N" MEAN*F=6.2 STD="SD"*F=4.2 MEDIAN MIN MAX), (ZTREATMENTCODE ALL="ALL GROUPS") /BOX=[LABEL="&MYTITLE" STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]]; KEYLABEL N=" "; CLASSLEV ZTREATMENTCODE /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; KEYWORD ALL N MEAN STD MEDIAN MIN MAX /STYLE=[FONT_SIZE=1.5 FOREGROUND=BLACK BACKGROUND=WHITE]; RUN; %MEND;

  38. Summary: • SAS macros can make programming much easier. • Not all programs are enhanced by SAS macros. • If you do choose to incorporate SAS macros: • Syntax is crucial!! • Debugging can be tricky!! • Efficiency can be tremendously improved!

  39. Suggestions for starting off: • Always write them one piece at a time • Write your program using standard SAS code first. • After debugging that, add %MACRO and %MEND. • Then add your parameters.

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