BMTRY 789 Lecture 10: SAS MACRO Facility Annie N. Simpson, MSc.

What's a MACRO? MACRO: a rule or pattern that specifies how a certain input sequence should be mapped to an output sequence according to a defined procedure. (Wikipedia)

Facts about Macros SAS macro code is separate from SAS code Allows you to do repetitive assignments where the only difference is a variable (s) Enables great flexibility in SAS programming and saves time

Macros from beginning to %Mend 1. The % typically identifies a macro command 2. Code enclosed within %MACRO and %MEND are viewed by SAS as a program 3. You can (almost) freely mix regular SAS code with Macro code 4. Once you define a macro program, you then need to “call” (or invoke) it 5. You call a macro by %«macro name» (you don't use the word MACRO when you call it...only when you are defining it)

MACRO VARIABLE Macro variables are either defined by a %LET statement or as parameters within a macro program A macro variable is referenced in your program by preceding the macro variable name with an ampersand (&).

LAB DATA Example Consider you want to create BOXPLOTS for several lab tests: Hemoglobin, Hematocrit, Platelets Each BOXPLOT should have its own title and axis. Of course, we will use SAS for this

Lab Data ObsTESTRESULT_N_NUMvisit 1Hematocrit45.5SC 2Hematocrit51SC 3Hematocrit45.4SC 4Hematocrit44.7SC 5Hematocrit50SC 6Hematocrit46.9SC 7Hematocrit45.9SC 8Hematocrit42.8SC 9Hematocrit42.1SC 10Hematocrit55.9SC 11Hematocrit43.6SC 12Hematocrit44.6SC 13Hematocrit39.2SC 14Hematocrit47.5SC 15Hematocrit45.5SC 16Hematocrit47.9SC 17Hematocrit44.6SC

Sample SAS MACRO for BOXPLOTS

Adding Parameters to Macros Once you identify potential parameters, list them out in parenthesis separated by a comma in the MACRO declaration When you call the MACRO, you pass the values to the MACRO again in parenthesis separated by commas

What happens? What happens if you run this program? ?? Let's check the log

Don’t forget to CALL! Nothing happened because we didn't CALL the macro Here's what the log reads after we call %labs

RESULT

SAS LOG WILL LOOK DIFFERENT Note, in the SAS MACRO log, you do not get the NOTES interspersed with the PROC statements Why? Because the entire MACRO gets compiled into a bundle of code You can “look” into the bundle of code by using the MPRINT system option

%Put On occasion, you may want to “look inside” a macro variable to see what value is stored This often occurs during debugging parameters You accomplish this by the %Put statement followed by the variable name %Put writes values to the SAS LOG There are also special %Put statements: %put _all_ %put _user_ %put _local_ %put _global_

%LET Creates a macro variable and assigns it a value %LET can be used inside or outside of a macro program Syntax %LET macro-variable = ; (CAN BE A STRING OF WORDS)

EXAMPLE 2: Using %LET, %DO and %SCAN

Conclusions MACROS save time Necessary when have a large number of variables. Imagine running a regression for every variable when you have 100+ variables! Programs are reusable and easier to understand.