Skip to main content
Use the gamma function in APL to compute the gamma function of a numeric value. For positive integers, gamma(n) equals (n-1)!. The gamma function generalizes the factorial to real and complex numbers. gamma is useful in statistical calculations such as computing combinatorial coefficients, probability distributions, and Bayesian models. In observability, you might use it in custom anomaly scoring or when implementing statistical tests directly in APL.

​
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.
Splunk SPL doesn’t include a built-in gamma() function. You need to implement the gamma function using external lookup tables or the Machine Learning Toolkit.
| eval gamma_val = null()
Standard SQL does not define a GAMMA() function. You typically implement it in application code or through database-specific extensions.
-- No standard SQL equivalent; use application code
SELECT NULL AS gamma_val FROM logs

​
Usage

​
Syntax

gamma(x)

​
Parameters

NameTypeRequiredDescription
xrealYesThe input value. Must not be zero or a negative integer.

​
Returns

  • The gamma function of x.
  • Returns null when x is zero or a negative integer.
  • For large inputs, the result may overflow to infinity.

​
Example

Use gamma to compute the gamma function value for a request duration in seconds. Query 
['sample-http-logs']
| where req_duration_ms > 0
| extend duration_s = req_duration_ms / 1000.0
| where duration_s < 5
| extend gamma_val = gamma(duration_s)
| where isfinite(gamma_val)
| project _time, id, req_duration_ms, gamma_val
Run in Playground Output
_timeidreq_duration_msgamma_val
2024-11-14 10:00:00user-11000.01.0000
2024-11-14 10:01:00user-22000.01.0000
2024-11-14 10:02:00user-33000.02.0000
  • loggamma: Returns the natural log of the absolute gamma function value. Use it to avoid numeric overflow when working with large inputs.
  • log: Returns the natural logarithm. Use it when you want to work in log space rather than applying gamma directly.
  • exp: Returns e^x. Use it to exponentiate log-space results from loggamma back to the original scale.
  • pow: Raises a value to a power. Use it for simpler power calculations that don’t require the general gamma function.
  • isfinite: Returns whether a value is finite. Use it to filter out overflow results from gamma on large inputs.