log2

Use the log2 function in APL to compute the base-2 logarithm of a positive numeric value. The function is the inverse of exp2.

log2 is useful when working with data measured on a binary scale, such as memory sizes, network packet lengths, or binary tree structures. Because each unit increase in log2(x) corresponds to a doubling of x, log2 is a natural choice for analyzing values that grow or shrink by factors of two. You can also use it to compute geometric means in base-2 space.

Usage

Syntax

log2(x)

Parameters

Returns

• The base-2 logarithm of x.
• null if x is negative, zero, or can't be converted to a real value.

Example

Use log2 to express request durations on a binary log scale where each unit represents a doubling.

Query

['sample-http-logs']
| where req_duration_ms > 0
| extend log2_duration = log2(req_duration_ms)
| project _time, id, req_duration_ms, log2_duration

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Output

List of related functions

• exp2: Returns 2^x. Use it as the inverse of log2.
• log: Returns the natural logarithm. Use it when you prefer the natural base rather than base-2.
• log10: Returns the base-10 logarithm. Use it for order-of-magnitude analysis instead of binary analysis.
• pow: Raises a value to a power. Use it to compute powers of two directly as an alternative to exp2.
• round: Rounds a value. Use it after log2 to bucket data into binary power groups.

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