LOG function

Calculates the logarithm of an expression using a specified base and returns that logarithm as a DECIMAL value.

Syntax 

 

LOG ( expression [ , base ] )

expression

A decimal expression that you want the logarithm of.

base

A numeric expression that is the base you want to use. If you do not specify a base, LOG returns the natural logarithm, base (e). The base must be greater than 1.

Example 

This procedure prompts the user for a base and a number, and then displays the log of the number. The VALIDATE option on the UPDATE statement ensures that the user enters a base value greater than 1 and a number greater than 0.

 

r-log.p

DEFINE VARIABLE base   AS DECIMAL NO-UNDO FORMAT ">>>,>>>.9999". DEFINE VARIABLE number AS DECIMAL NO-UNDO.   REPEAT: UPDATE base VALIDATE(base > 1, "Base must be greater than 1"). REPEAT: UPDATE number VALIDATE(number > 0, "Number must be positive"). DISPLAY number LOG(number, base) LABEL "LOG(NUMBER, BASE)". END. END.

Notes 

The LOG function is accurate to approximately 10 decimal places.

After converting the base and exponent to floating-point format, the LOG function uses standard system routines. On some machines, the logarithm routines do not handle large numbers well and might cause your terminal to hang.