10 SAS Macro Interview Questions and Answers

SAS Macro is a powerful feature of the SAS programming language that allows for dynamic code generation and automation of repetitive tasks. It is widely used in data analysis, reporting, and data manipulation, making it an essential skill for professionals working with large datasets and complex data workflows. Mastery of SAS Macro can significantly enhance productivity and efficiency in data-related projects.

This article provides a curated selection of interview questions focused on SAS Macro, designed to help you demonstrate your proficiency and problem-solving abilities. By familiarizing yourself with these questions and their answers, you will be better prepared to showcase your expertise and stand out in technical interviews.

SAS Macro Interview Questions and Answers

1. What is a SAS Macro and why is it used?

A SAS Macro is a tool within the SAS programming environment that automates repetitive tasks and dynamically generates SAS code. Macros are useful for executing the same code multiple times with slight variations, leading to more efficient and maintainable code. They are defined using the %MACRO statement and can include macro variables and functions, allowing for greater flexibility and reusability.

Example:

%macro print_data(dataset);
    proc print data=&dataset;
    run;
%mend print_data;

%print_data(sashelp.class);
%print_data(sashelp.cars);

In this example, the macro print_data prints any dataset passed to it, with the macro variable &dataset replaced by the actual dataset name when the macro is called.

2. Explain the difference between %LET and CALL SYMPUT in SAS Macros.

In SAS Macros, %LET and CALL SYMPUT both create and assign values to macro variables but differ in their usage.

• %LET is a compile-time statement used when the value is known at compile time.
• CALL SYMPUT is a data step function used at run time when the value is determined during a data step.

Example:

/* Using %LET */
%let var1 = 10;
%put &var1; /* Output: 10 */

/* Using CALL SYMPUT */
data _null_;
    call symput('var2', '20');
run;
%put &var2; /* Output: 20 */

3. Write a simple macro that takes two parameters and prints their sum.

A simple macro can take parameters and perform operations based on those parameters. Below is an example of a SAS macro that takes two parameters and prints their sum.

%macro sum_two_numbers(num1, num2);
    %let result = %eval(&num1 + &num2);
    %put The sum of &num1 and &num2 is &result;
%mend sum_two_numbers;

%sum_two_numbers(5, 10);

4. Write a macro that loops through a list of values and performs a calculation on each value.

To loop through a list of values and perform a calculation on each value, use the %DO loop within a macro.

Example:

%macro calculate(values);
    %let n = %sysfunc(countw(&values));
    %do i = 1 %to &n;
        %let value = %scan(&values, &i);
        %let result = %eval(&value * 2); /* Example calculation: multiply by 2 */
        %put Value: &value, Result: &result;
    %end;
%mend calculate;

%calculate(1 2 3 4 5);

5. Explain the use of %IF-%THEN/%ELSE statements in macros. Provide an example.

The %IF-%THEN/%ELSE statements in SAS macros allow for conditional logic, enabling dynamic decision-making based on macro variable values or expressions.

Example:

%macro check_value(val);
    %if &val > 10 %then %do;
        %put The value is greater than 10;
    %end;
    %else %do;
        %put The value is 10 or less;
    %end;
%mend check_value;

%check_value(15);
%check_value(5);

6. How can you pass a dataset name as a parameter to a macro and use it within the macro?

To pass a dataset name as a parameter to a macro, define the macro with a parameter and use that parameter within the macro code.

Example:

%macro print_dataset(data);
    proc print data=&data;
    run;
%mend print_dataset;

%print_dataset(sashelp.class);

In this example, the macro print_dataset takes one parameter data, representing the dataset name. The proc print statement uses the &data macro variable to refer to the dataset passed as a parameter.

7. Write a macro that conditionally executes different code blocks based on the value of a macro variable.

Conditional execution within a macro allows different code blocks to be executed based on a macro variable’s value, using %IF-%THEN-%ELSE statements.

Example:

%macro conditional_execute(condition);
    %if &condition = 1 %then %do;
        %put Condition is 1;
        /* Additional code for condition 1 */
    %end;
    %else %if &condition = 2 %then %do;
        %put Condition is 2;
        /* Additional code for condition 2 */
    %end;
    %else %do;
        %put Condition is neither 1 nor 2;
        /* Additional code for other conditions */
    %end;
%mend conditional_execute;

%conditional_execute(1);
%conditional_execute(2);
%conditional_execute(3);

8. Explain the concept of macro quoting functions and provide an example of their use.

Macro quoting functions in SAS handle special characters and mnemonics within macro variables, ensuring they are treated as literal text rather than interpreted as part of the macro language. This is useful when dealing with characters like %, &, or other symbols with special meanings.

Common macro quoting functions include %STR, %NRSTR, %QUOTE, and %NRQUOTE.

Example:

%let special_char = %str(Hello%World);
%put &special_char; /* Output: Hello%World */

%let special_char_unquoted = Hello%World;
%put &special_char_unquoted; /* This will cause an error */

In this example, %STR is used to mask the % character within the macro variable special_char. Without using %STR, the macro processor would interpret the % character as the beginning of a macro variable or function, leading to an error.

9. How would you create a macro that generates multiple datasets based on input parameters?

By using macros, you can generate multiple datasets based on input parameters, which is useful for performing similar operations on different data subsets.

Example:

%macro generate_datasets(prefix, start, end);
    %do i = &start %to &end;
        data &prefix&i;
            set sashelp.class;
            where age = &i;
        run;
    %end;
%mend generate_datasets;

%generate_datasets(dataset, 12, 15);

In this example, the macro generate_datasets takes three parameters: prefix, start, and end. It generates datasets with names based on the prefix and a range of numbers from start to end.

10. Write a macro that includes error handling to manage unexpected inputs.

Error handling in SAS Macros manages unexpected inputs and ensures correct execution. By incorporating error handling, you can provide meaningful messages to the user and prevent incorrect results. This can be implemented using conditional statements and the %PUT statement to display error messages.

Example:

%macro check_input(value);
    %if &value = %then %do;
        %put ERROR: Input value is missing.;
        %return;
    %end;
    %else %if %sysfunc(notdigit(&value)) %then %do;
        %put ERROR: Input value is not a number.;
        %return;
    %end;
    %else %do;
        %put Input value is valid: &value;
    %end;
%mend check_input;

%check_input(); /* Missing input */
%check_input(abc); /* Non-numeric input */
%check_input(123); /* Valid input */