> ## 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If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback: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/log10",
  "feedback": "Description of the issue"
}
```

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

</AgentInstructions>

# log10

> This page explains how to use the log10 function in APL.

Use the `log10` function in APL to compute the common (base-10) logarithm of a positive numeric value. The function returns `null` for zero or negative inputs.

`log10` is useful for order-of-magnitude analysis. Because each unit increase in `log10(x)` represents a tenfold increase in `x`, you can use it to compare values that span multiple orders of magnitude, build decibel-scale metrics, or bucket data by powers of ten. It's also the basis for recovering values with `exp10`.

## 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, `log10()` works identically: it returns the base-10 logarithm.

    <CodeGroup>
      ```sql Splunk example theme={null}
      | eval log10_duration = log10(req_duration_ms)
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend log10_duration = log10(req_duration_ms)
      ```
    </CodeGroup>
  </Accordion>

  <Accordion title="ANSI SQL users">
    In ANSI SQL, `LOG10()` is a standard function in SQL Server and PostgreSQL with the same behavior as APL's `log10`.

    <CodeGroup>
      ```sql SQL example theme={null}
      SELECT LOG10(req_duration_ms) AS log10_duration FROM logs
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend log10_duration = log10(req_duration_ms)
      ```
    </CodeGroup>
  </Accordion>
</AccordionGroup>

## Usage

### Syntax

```kusto theme={null}
log10(x)
```

### Parameters

| Name | Type | Required | Description                     |
| ---- | ---- | -------- | ------------------------------- |
| `x`  | real | Yes      | A positive real number (x > 0). |

### Returns

* The base-10 logarithm of `x`.
* `null` if `x` is negative, zero, or cannot be converted to a real value.

## Example

Use `log10` to express request durations on a base-10 log scale where each integer step represents an order of magnitude.

**Query**

```kusto theme={null}
['sample-http-logs']
| where req_duration_ms > 0
| extend log10_duration = log10(req_duration_ms)
| project _time, id, req_duration_ms, log10_duration
```

[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%20extend%20log10_duration%20%3D%20log10%28req_duration_ms%29%20%7C%20project%20_time%2C%20id%2C%20req_duration_ms%2C%20log10_duration%22%7D)

**Output**

| \_time              | id     | req\_duration\_ms | log10\_duration |
| ------------------- | ------ | ----------------- | --------------- |
| 2024-11-14 10:00:00 | user-1 | 1.0               | 0.0000          |
| 2024-11-14 10:01:00 | user-2 | 100.0             | 2.0000          |
| 2024-11-14 10:02:00 | user-3 | 10000.0           | 4.0000          |

## List of related functions

* [exp10](/apl/scalar-functions/mathematical-functions/exp10): Returns 10^x. Use it as the inverse of `log10` to recover original values.
* [log](/apl/scalar-functions/mathematical-functions/log): Returns the natural logarithm. Use it when you want the mathematically natural base rather than base-10.
* [log2](/apl/scalar-functions/mathematical-functions/log2): Returns the base-2 logarithm. Use it for binary-scale analysis.
* [pow](/apl/scalar-functions/mathematical-functions/pow): Raises a value to a power. Use it to compute powers of 10 directly as an alternative to `exp10`.
* [round](/apl/scalar-functions/mathematical-functions/round): Rounds a value. Use it after `log10` to bucket values by integer order of magnitude.