pi

Use the pi function in APL to return the mathematical constant π (pi), approximately equal to 3.14159265358979. The function takes no arguments and always returns the same double-precision floating-point value.

pi is most commonly used to construct radian angle values for trigonometric functions. For example, you can encode the hour of day as a cyclic coordinate using (hour * 2 * pi()) / 24, or convert between degrees and radians using radians = degrees * pi() / 180.

Usage

Syntax

pi()

Parameters

None.

Returns

The double-precision value of π: approximately 3.14159265358979.

Example

Use pi to encode the hour of day as a cyclic angle for time-based analysis.

Query

['sample-http-logs']
| extend hour_angle = (hourofday(_time) * 2 * pi()) / 24
| extend sin_hour = sin(hour_angle)
| extend cos_hour = cos(hour_angle)
| project _time, id, sin_hour, cos_hour

Output

List of related functions

• sin: Returns the sine of an angle in radians. Combine with pi to encode cyclic signals.
• cos: Returns the cosine of an angle in radians. Use together with sin and pi for cyclic coordinate encoding.
• radians: Converts degrees to radians. Use it as an alternative to manually multiplying by pi() / 180.
• degrees: Converts radians to degrees. Use it to express results from inverse trig functions in degrees instead of radians.
• atan2: Returns the angle in radians between two coordinates. Its output range is (-π, π], so pi is a natural companion.

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