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BMTRY 789 Lecture 10: SAS MACRO Facility

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.

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BMTRY 789 Lecture 10: SAS MACRO Facility

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

  2. 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)

  3. 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

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

  5. 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 (&).

  6. 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

  7. Lab Data

  8. Sample SAS MACRO for BOXPLOTS

  9. 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

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

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

  12. RESULT

  13. 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

  14. %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_

  15. %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 =<value>; (CAN BE A STRING OF WORDS)

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

  17. 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.

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