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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.

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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.
In Splunk SPL, log10() works identically: it returns the base-10 logarithm.
| eval log10_duration = log10(req_duration_ms)
In ANSI SQL, LOG10() is a standard function in SQL Server and PostgreSQL with the same behavior as APL’s log10.
SELECT LOG10(req_duration_ms) AS log10_duration FROM logs

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Usage

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Syntax

log10(x)

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Parameters

NameTypeRequiredDescription
xrealYesA positive real number (x > 0).

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Returns

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

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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
Run in Playground Output
_timeidreq_duration_mslog10_duration
2024-11-14 10:00:00user-11.00.0000
2024-11-14 10:01:00user-2100.02.0000
2024-11-14 10:02:00user-310000.04.0000
  • 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.