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`]("https"://documentation.sas.com/?cdcId=pgmsascdc&cdcVersion=9.4_3.5&docsetId=lefunctionsref&docsetTarget=p0l7s11dwvzfq5n1wnw997dye8fx.htm&locale=en#p12c30o3nnxlu7n186c3ytfju9bg) 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.

```sas
data Ex2;
    x=constant('E');
    y=log(constant('E'));
    put x= y=;
run;```
**"Output":**

![Image](../../assets/2021/03/img_6064045371989.png)
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;```
**"Output":**

<p id="duNRTzn">![Determine the log of a variable in SAS ](../../assets/2021/03/img_6063ff519d227.png)</p>

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