Using %EVAL and %SYSEVALF Functions

This SAS^© script illustrates how to use the %EVAL and %SYSEVALF macro functions to perform arithmetic operations on macro variables. It starts with a simple salary difference calculation using %EVAL, highlighting its suitability for integers. Then, it emphasizes the limitation of %EVAL with decimal numbers by introducing a floating-point value that causes an error. Finally, it presents %SYSEVALF as the robust solution for handling calculations with floating-point numbers, ensuring precision and avoiding errors.

Data Analysis

Type : CREATION_INTERNE

Data consists of numeric macro variables (%salary1, %salary2) defined directly within the script, without any external data source or SASHELP data.

1 Code Block

MACRO Data

Explanation :
This block initializes two macro variables, `salary1` and `salary2`, with integer values. It then uses the `%EVAL` macro function to calculate the difference between these two salaries and stores the result in a new macro variable `salary_diff`. The value of `salary_diff` is displayed in the SAS log using `%PUT`. This case works because `%EVAL` is suitable for integer operations.

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1	%let salary1=25000;
2	%let salary2=27000;
3	%let salary_diff = %eval(&salary2 - &salary1);
4	%put The salary difference is &salary_diff;

2 Code Block

MACRO

Explanation :
In this block, `salary2` is modified to include a decimal value. The difference calculation is attempted again with `%EVAL`. However, `%EVAL` is designed for integer operations and cannot correctly handle floating-point numbers. This would result in an error or warning in the SAS log, as `%EVAL` attempts to convert the decimal value to an integer, which is a limitation of this function.

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1	%let salary1=25000;
2	%let salary2=27050.45;
3	%let salary_diff = %eval(&salary2 - &salary1);
4	%put The salary difference is &salary_diff;

3 Code Block

MACRO

Explanation :
This block corrects the previous problem by using the `%SYSEVALF` macro function. `%SYSEVALF` is specifically designed to evaluate arithmetic expressions that can include floating-point numbers. It allows for precise calculation of the salary difference, even when the operands are decimals, without generating data type-related errors or warnings in the SAS log.

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1	%let salary1=25000;
2	%let salary2=27050.45;
3	%let salary_diff = %sysevalf(&salary2 - &salary1);
4	%put The salary difference is &salary_diff;

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Copyright Info : Practice 3: Use the %EVAL and %SYSEVALF Functions Lesson 2 - Using Macro Functions SAS Macro Language 1: Essentials

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