Feb 11, 2010

SAS Macro functions - %eval() and %sysevalf()

The %EVAL function evaluates integer arithmetic or logical expressions. %EVAL operates by converting its argument from a character value to a numeric or logical expression. Then, it performs the evaluation. Finally, %EVAL converts the result back to a character value and returns that value.
Operands that contain a period character cause an error when they are part of an integer arithmetic expression. The following examples show correct and incorrect usage, respectively:
%let d=%eval(10+20);     /* Correct usage */
%let d=%eval(10.0+20.0); /* Incorrect usage */
When %EVAL encounters a value containing a period, it displays an error message about finding a character operand where a numeric operand is required.
%let a=1+2;
%let b=10*3;
%let c=5/3;
%let eval_a=%eval(&a);
%let eval_b=%eval(&b);
%let eval_c=%eval(&c);
%put &a is &eval_a;
%put &b is &eval_b;
%put &c is &eval_c;
The Log produces…
The %SYSEVALF function evaluates arithmetic and logical expressions using floating-point arithmetic and returns a value that is formatted using the BEST32. format. The result of the evaluation is always text. % SYSEVALF is the only macro function that can evaluate logical expressions that contain floating point or missing values. Specifying a conversion type can prevent problems when %SYSEVALF returns missing or floating point values to macro expressions or macro variables that are used in other macro expressions that require an integer value.
Syntax: %SYSEVALF(expression<, conversion-type>)
Taking an example…
%let a=100;
%let b=101.590;
%let x=%sysevalf(&a+&b);
%let y=%sysevalf(&a +&b, boolean);
%let z=%sysevalf(&a +&b, ceil);
%let v=%sysevalf(&a +&b, floor);
%let w=%sysevalf(&a +&b, int);
%put The result with SYSEVALF is: &x;
%put  The BOOLEAN value is: &y;
%put  The CEIL value is: &z;
%put  The FLOOR value is: &v;
%put  The INTEGER value is: &w;
The Log produces…

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