sqrt

sqrt is useful whenever you want to compress large numeric ranges, compute root-mean-square values, normalize metrics, or undo a squared transformation. It's equivalent to pow(x, 0.5) but is more concise for the square-root case.

If the input is negative, sqrt returns NaN (Not a Number). APL represents NaN as null in query results. Use isnan to filter these values before aggregating or charting.

Usage#

Syntax#

sqrt(x)

Parameters#

Name	Type	Required	Description
`x`	real	Yes	The value to compute the square root of. Must be non-negative for a defined result.

Returns#

Returns the square root of x.

If x is negative, the function returns NaN, which APL represents as null in query results. Use isnan to check for this condition.

Examples#

Compute the square root of request duration#

Use sqrt to normalize request durations by taking their square root, compressing the range of large values.

Query

['sample-http-logs']
| extend root_duration = sqrt(req_duration_ms)
| project _time, id, req_duration_ms, root_duration
| order by root_duration desc

Run in Playground

Output

_time	id	req_duration_ms	root_duration
2024-11-14 10:00:00	user-1	1600.0	40.0
2024-11-14 10:01:00	user-2	400.0	20.0
2024-11-14 10:02:00	user-3	25.0	5.0

Detect NaN from negative inputs#

When input values are negative, sqrt returns NaN. APL displays NaN as null. Use isnan to identify and handle these rows.

Query

['sample-http-logs']
| extend shifted = req_duration_ms - 500
| extend root_shifted = sqrt(shifted)
| extend is_invalid = isnan(root_shifted)
| project _time, id, shifted, root_shifted, is_invalid

Run in Playground

Output

_time	id	shifted	root_shifted	is_invalid
2024-11-14 10:00:00	user-1	700.0	26.46	false
2024-11-14 10:01:00	user-2	-200.0	null	true
2024-11-14 10:03:00	user-3	-50.0	null	true

pow: Raises a value to an arbitrary power. sqrt(x) is equivalent to pow(x, 0.5).
isnan: Returns true when a value is NaN. Use it to detect null results from sqrt on negative inputs.
abs: Returns the absolute value. Use it to ensure inputs are non-negative before passing them to sqrt.
exp: Returns e^x. Use it when the inverse operation of log is needed rather than a root.
log: Returns the natural logarithm. Use it alongside sqrt when working in log space.

Other query languages#

Splunk SPL users

In Splunk SPL, sqrt() works identically: it takes a single numeric argument and returns its square root.

Splunk example

| eval root_duration = sqrt(req_duration_ms)

APL equivalent

['sample-http-logs']
| extend root_duration = sqrt(req_duration_ms)

ANSI SQL users

In ANSI SQL, SQRT() is a standard built-in function with the same semantics as in APL.

SQL example

SELECT SQRT(req_duration_ms) AS root_duration FROM logs