ClickHouse/docs/en/sql-reference/aggregate-functions/reference/entropy.md

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entropy

Calculates Shannon entropy of a column of values.

Syntax

entropy(val)

Arguments

• val — Column of values of any type.

Returned value

• Shannon entropy.

Type: Float64.

Example

Query:

CREATE TABLE entropy (`vals` UInt32,`strings` String) ENGINE = Memory;

INSERT INTO entropy VALUES (1, 'A'), (1, 'A'), (1,'A'), (1,'A'), (2,'B'), (2,'B'), (2,'C'), (2,'D');

SELECT entropy(vals), entropy(strings) FROM entropy;

Result:

┌─entropy(vals)─┬─entropy(strings)─┐
│             1 │             1.75 │
└───────────────┴──────────────────┘