> ## 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If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback: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/exp2",
  "feedback": "Description of the issue"
}
```

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

</AgentInstructions>

# exp2

> This page explains how to use the exp2 function in APL.

Use the `exp2` function in APL to compute the base-2 exponential of a value: 2^x. It's the inverse of the base-2 logarithm function `log2`.

`exp2` is useful when you work with data measured on a binary scale, such as memory sizes, network bandwidths, or binary tree depths. You can also use it to reverse a `log2` transformation and recover values on the original scale.

## 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">
    Splunk SPL doesn't include a built-in `exp2()` function. You compute it as `pow(2, x)`.

    <CodeGroup>
      ```sql Splunk example theme={null}
      | eval result = pow(2, x)
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend result = exp2(x)
      ```
    </CodeGroup>
  </Accordion>

  <Accordion title="ANSI SQL users">
    Standard SQL does not define `EXP2()`. You compute it using `POWER(2, x)`.

    <CodeGroup>
      ```sql SQL example theme={null}
      SELECT POWER(2, x) AS result FROM logs
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend result = exp2(x)
      ```
    </CodeGroup>
  </Accordion>
</AccordionGroup>

## Usage

### Syntax

```kusto theme={null}
exp2(x)
```

### Parameters

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

### Returns

The base-2 exponential of `x`: 2^x.

## Example

Use `exp2` to recover the geometric mean of request durations from a log2-transformed average.

**Query**

```kusto theme={null}
['sample-http-logs']
| where req_duration_ms > 0
| summarize geometric_mean = exp2(avg(log2(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%20exp2%28avg%28log2%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

* [log2](/apl/scalar-functions/mathematical-functions/log2): Returns the base-2 logarithm. Use it as the inverse of `exp2`.
* [exp](/apl/scalar-functions/mathematical-functions/exp): Returns e^x. Use it for natural-log-scale transformations instead of base-2.
* [exp10](/apl/scalar-functions/mathematical-functions/exp10): Returns 10^x. Use it for base-10 (order-of-magnitude) scales.
* [pow](/apl/scalar-functions/mathematical-functions/pow): Raises any base to a power. Use it when neither e, 2, nor 10 is the intended base.
* [log](/apl/scalar-functions/mathematical-functions/log): Returns the natural logarithm. Use it together with `exp` for natural-log-scale analysis.