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If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback: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

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

</AgentInstructions>

# sign

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

Use the `sign` function in APL to return the sign of a numeric expression: +1 for positive values, 0 for zero, and -1 for negative values.

`sign` is useful when you care about the direction of a value rather than its magnitude. For example, you can use `sign` to classify whether a request latency is above or below a baseline, detect whether a metric is trending up or down, or encode deviations as ternary labels for downstream classification.

## 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 uses `signum()` rather than `sign()`. The semantics are identical: it returns +1, 0, or -1.

    <CodeGroup>
      ```sql Splunk example theme={null}
      | eval direction = signum(deviation)
      ```

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

  <Accordion title="ANSI SQL users">
    In ANSI SQL, `SIGN()` works the same as in APL: it returns +1, 0, or -1 for positive, zero, and negative inputs respectively.

    <CodeGroup>
      ```sql SQL example theme={null}
      SELECT SIGN(deviation) AS direction FROM logs
      ```

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

## Usage

### Syntax

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

### Parameters

| Name | Type | Required | Description    |
| ---- | ---- | -------- | -------------- |
| `x`  | real | Yes      | A real number. |

### Returns

* `+1` if `x` is positive.
* `0` if `x` is zero.
* `-1` if `x` is negative.

## Example

Use `sign` to classify each request as faster (-1), on-target (0), or slower (+1) than a 200 ms baseline.

**Query**

```kusto theme={null}
['sample-http-logs']
| extend deviation = req_duration_ms - 200.0
| extend deviation_sign = sign(deviation)
| project _time, id, req_duration_ms, deviation_sign
```

[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%20extend%20deviation%20%3D%20req_duration_ms%20-%20200.0%20%7C%20extend%20deviation_sign%20%3D%20sign%28deviation%29%20%7C%20project%20_time%2C%20id%2C%20req_duration_ms%2C%20deviation_sign%22%7D)

**Output**

| \_time              | id     | req\_duration\_ms | deviation\_sign |
| ------------------- | ------ | ----------------- | --------------- |
| 2024-11-14 10:00:00 | user-1 | 450.0             | 1               |
| 2024-11-14 10:01:00 | user-2 | 80.0              | -1              |
| 2024-11-14 10:02:00 | user-3 | 200.0             | 0               |

## List of related functions

* [abs](/apl/scalar-functions/mathematical-functions/abs): Returns the absolute value. Use it to get magnitude when direction from `sign` is not enough.
* [round](/apl/scalar-functions/mathematical-functions/round): Rounds a value. Use it to normalize values before comparing signs.
* [not](/apl/scalar-functions/mathematical-functions/not): Reverses a boolean. Use it alongside `sign` for boolean-style conditions on direction.
* [pow](/apl/scalar-functions/mathematical-functions/pow): Raises a value to a power. Use `pow(x, 2)` together with `sign(x)` to keep direction while amplifying magnitude.
* [sqrt](/apl/scalar-functions/mathematical-functions/sqrt): Returns the square root. Use it to compute magnitude, and `sign` to determine direction, when you need a signed root.