log10

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.
null if x is 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_duration

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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

exp10: Returns 10^x. Use it as the inverse of log10 to 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 log10 to bucket values by integer order of magnitude.

Other query languages#

Splunk SPL users

In Splunk SPL, log10() works identically: it returns the base-10 logarithm.

Splunk example

| eval log10_duration = log10(req_duration_ms)

APL equivalent

['sample-http-logs']
| extend log10_duration = log10(req_duration_ms)

ANSI SQL users

In ANSI SQL, LOG10() is a standard function in SQL Server and PostgreSQL with the same behavior as APL's log10.

SQL example

SELECT LOG10(req_duration_ms) AS log10_duration FROM logs