Determine the log of a variable in SAS1 min read

Determine the log of a variable in any base

There are multiple logarithmic functions available to determine the log of a variable in SAS. The most used log functions are the natural and common log functions.

The natural LOG function returns the natural (base e) logarithm.

data Ex1;
	x=log(1);
	put x=;
run;

In Example 1, with the input of 1, SAS returns the expected value of 0 and using Euler’s Number approximation of 2.71828, the result y is very close to 1.

You can use the CONSTANT function that will return the value of a mathematical constant. For Euler’s Number, the notation is ‘E’. From reviewing the log using CONSTANT(‘E’), the expected value of 1 is returned.

data Ex2;
	x=constant('E');
	y=log(constant('E'));
	put x= y=;
run;

For the common log, the SAS function is LOG10. The LOG2 function returns the binary logarithm, or base 2.

Program to Determine the log of a variable in any base

You can compute the log of a variable in any base using the LOG function and the property.

logB(X)=log(X) / log10(B)

X is the variable whose log will be determined. B is the base of the log that will be determined and Y is the log, base b, of x.

data ex1;
	b=6;

	do i=1 to 10;
		x=int(ranuni(12345)*100);

		/* Y equals the LOG, base B, of X*/
		y=LOG10(x)/LOG10(b);
		output;
	end;
run;