math.log() - Lua | Version 5.4 Docs

The math.log function returns the logarithm of a number in the specified base. If no base is provided, it returns the natural logarithm (base e) of the number.

Syntax

math.log(x [, base])

Parameters

x: A number greater than 0.
base (optional): The base of the logarithm. If not specified, the base is e.

Return value

The logarithm of x in the specified base. If x is ≤ 0, the function returns NaN.

Description

math.log computes the logarithm of x. By default, it uses the natural logarithm (base e). To compute the logarithm in a different base, provide the base as the second argument. The relationship for logarithms can be expressed as:

Examples

Using `math.log()`

print(math.log(-1))       -- NaN
print(math.log(0))        -- NaN
print(math.log(1))        -- 0
print(math.log(10))       -- 2.302585092994046
print(math.log(math.huge)) -- Infinity

Using `math.log()` with a different base

To calculate the logarithm of y with base x:

function getBaseLog(x, y)
    return math.log(y) / math.log(x)
end

print(getBaseLog(10, 1000)) -- 2.9999999999999996 (approx. 3)