# Function log1p Calculate the logarithm of a `value+1`. For matrices, the function is evaluated element wise. ## Syntax ```js math.log1p(x) math.log1p(x, base) ``` ### Parameters Parameter | Type | Description --------- | ---- | ----------- `x` | number | BigNumber | Complex | Array | Matrix | Value for which to calculate the logarithm of `x+1`. `base` | number | BigNumber | Complex | Optional base for the logarithm. If not provided, the natural logarithm of `x+1` is calculated. Default value: e. ### Returns Type | Description ---- | ----------- number | BigNumber | Complex | Array | Matrix | Returns the logarithm of `x+1` ## Examples ```js math.log1p(2.5) // returns 1.252762968495368 math.exp(math.log1p(1.4)) // returns 2.4 math.pow(10, 4) // returns 10000 math.log1p(9999, 10) // returns 4 math.log1p(9999) / math.log(10) // returns 4 ``` ## See also [exp](exp.md), [log](log.md), [log2](log2.md), [log10](log10.md)