exp2

This page explains how to use the exp2 function in APL.

Use the exp2 function in APL to compute the base-2 exponential of a value: 2^x. It's the inverse of the base-2 logarithm function log2.

exp2 is useful when you work with data measured on a binary scale, such as memory sizes, network bandwidths, or binary tree depths. You can also use it to reverse a log2 transformation and recover values on the original scale.

Usage

Syntax

APL

exp2(x)

Parameters

Name	Type	Required	Description
`x`	real	Yes	The exponent value.

Returns

The base-2 exponential of x: 2^x.

Example

Use exp2 to recover the geometric mean of request durations from a log2-transformed average.

Query

APLRun in Playground

['sample-http-logs']
| where req_duration_ms > 0
| summarize geometric_mean = exp2(avg(log2(req_duration_ms))) by bin(_time, 1h)
| project _time, geometric_mean

Output

_time	geometric_mean
2024-11-14 10:00:00	85.3
2024-11-14 11:00:00	92.7
2024-11-14 12:00:00	78.1

log2: Returns the base-2 logarithm. Use it as the inverse of exp2.
exp: Returns e^x. Use it for natural-log-scale transformations instead of base-2.
exp10: Returns 10^x. Use it for base-10 (order-of-magnitude) scales.
pow: Raises any base to a power. Use it when neither e, 2, nor 10 is the intended base.
log: Returns the natural logarithm. Use it together with exp for natural-log-scale analysis.