You need to take the logarithm of a number.

For logarithms to base `e`

, use
`java.lang.Math`

’s `log( )`

function:

// Logarithm.java double someValue; // compute someValue... double log_e = Math.log(someValue);

For logarithms to other bases, use the identity that:

where `x`

is the number whose logarithm you want,
`n`

is any desired base, and `e`

is
the natural logarithm base. I have a simple
`LogBase`

class containing code that implements
this functionality:

// LogBase.java public static double log_base(double base, double value) { return Math.log(value) / Math.log(base); }

My `log_base`

function allows you to compute logs to
any positive base. If you have to perform a lot of logs to the same
base, it is more efficient to rewrite the code to cache the
`log(base)`

once. Here is an example of using
`log_base`

:

// LogBaseUse.java public static void main(String argv[]) { double d = LogBase.log_base(10, 10000); System.out.println("log10(10000) = " + d); } log10(10000) = 4.0

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