sign

Use the sign function in APL to return the sign of a numeric expression: +1 for positive values, 0 for zero, and -1 for negative values.

sign is useful when you care about the direction of a value rather than its magnitude. For example, you can use sign to classify whether a request latency is above or below a baseline, detect whether a metric is trending up or down, or encode deviations as ternary labels for downstream classification.

Usage

Syntax

sign(x)

Parameters

Returns

• +1 if x is positive.
• 0 if x is zero.
• -1 if x is negative.

Example

Use sign to classify each request as faster (-1), on-target (0), or slower (+1) than a 200 ms baseline.

Query

['sample-http-logs']
| extend deviation = req_duration_ms - 200.0
| extend deviation_sign = sign(deviation)
| project _time, id, req_duration_ms, deviation_sign

Output

List of related functions

• abs: Returns the absolute value. Use it to get magnitude when direction from sign isn't enough.
• round: Rounds a value. Use it to normalize values before comparing signs.
• not: Reverses a boolean. Use it alongside sign for boolean-style conditions on direction.
• pow: Raises a value to a power. Use pow(x, 2) together with sign(x) to keep direction while amplifying magnitude.
• sqrt: Returns the square root. Use it to compute magnitude, and sign to determine direction, when you need a signed root.

Other query languages