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.
Usage
Syntax
log10(x)Parameters
| Name | Type | Required | Description |
|---|---|---|---|
x | real | Yes | A positive real number (x > 0). |
Returns
- The base-10 logarithm of
x. nullifxis negative, zero, or can't 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
['sample-http-logs']
| where req_duration_ms > 0
| extend log10_duration = log10(req_duration_ms)
| project _time, id, req_duration_ms, log10_durationOutput
| _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: Returns 10^x. Use it as the inverse of
log10to recover original values. - log: Returns the natural logarithm. Use it when you want the mathematically natural base rather than base-10.
- log2: Returns the base-2 logarithm. Use it for binary-scale analysis.
- pow: Raises a value to a power. Use it to compute powers of 10 directly as an alternative to
exp10. - round: Rounds a value. Use it after
log10to bucket values by integer order of magnitude.