> ## Documentation Index
> Fetch the complete documentation index at: https://axiom.co/docs/llms.txt
> Use this file to discover all available pages before exploring further.

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

POST https://axiom.co/docs/feedback

```json
{
  "path": "/apl/scalar-functions/mathematical-functions/exp",
  "feedback": "Description of the issue"
}
```

Only submit feedback when you have something specific and actionable to report.

</AgentInstructions>

# exp

> This page explains how to use the exp function in APL.

Use the `exp` function in APL to compute the base-e exponential of a value: e^x. It's the inverse of the natural logarithm function `log`.

`exp` is useful when you work with log-transformed data and need to recover the original scale. For example, if you have computed the average of log-transformed latencies and want the geometric mean on the original scale, apply `exp` to the result. You can also use `exp` to model exponential growth or decay in metric data.

## For users of other query languages

If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.

<AccordionGroup>
  <Accordion title="Splunk SPL users">
    In Splunk SPL, `exp()` works the same way: it computes e^x for a numeric argument.

    <CodeGroup>
      ```sql Splunk example theme={null}
      | eval result = exp(log_value)
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend result = exp(log_value)
      ```
    </CodeGroup>
  </Accordion>

  <Accordion title="ANSI SQL users">
    In ANSI SQL, `EXP()` is a standard function with identical semantics.

    <CodeGroup>
      ```sql SQL example theme={null}
      SELECT EXP(log_value) AS result FROM logs
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend result = exp(log_value)
      ```
    </CodeGroup>
  </Accordion>
</AccordionGroup>

## Usage

### Syntax

```kusto theme={null}
exp(x)
```

### Parameters

| Name | Type | Required | Description         |
| ---- | ---- | -------- | ------------------- |
| `x`  | real | Yes      | The exponent value. |

### Returns

The base-e exponential of `x`: e^x.

## Example

Use `exp` to compute the geometric mean of request durations from log-transformed values.

**Query**

```kusto theme={null}
['sample-http-logs']
| where req_duration_ms > 0
| summarize geometric_mean = exp(avg(log(req_duration_ms))) by bin(_time, 1h)
| project _time, geometric_mean
```

[Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22%5B%27sample-http-logs%27%5D%20%7C%20where%20req_duration_ms%20%3E%200%20%7C%20summarize%20geometric_mean%20%3D%20exp%28avg%28log%28req_duration_ms%29%29%29%20by%20bin%28_time%2C%201h%29%20%7C%20project%20_time%2C%20geometric_mean%22%7D)

**Output**

| \_time              | geometric\_mean |
| ------------------- | --------------- |
| 2024-11-14 10:00:00 | 85.3            |
| 2024-11-14 11:00:00 | 92.7            |
| 2024-11-14 12:00:00 | 78.1            |

## List of related functions

* [log](/apl/scalar-functions/mathematical-functions/log): Returns the natural logarithm. Use it as the inverse of `exp` or to apply log transformations before aggregating.
* [exp2](/apl/scalar-functions/mathematical-functions/exp2): Returns 2^x. Use it instead of `exp` when working with binary (base-2) scales.
* [exp10](/apl/scalar-functions/mathematical-functions/exp10): Returns 10^x. Use it instead of `exp` when working with base-10 (decibel or order-of-magnitude) scales.
* [pow](/apl/scalar-functions/mathematical-functions/pow): Raises any base to a power. Use it when the base is not e, 2, or 10.
* [sqrt](/apl/scalar-functions/mathematical-functions/sqrt): Returns the square root. Use it for simpler power-of-0.5 calculations rather than `exp(0.5 * log(x))`.