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45 lines
905 B
Markdown
45 lines
905 B
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/entropy
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sidebar_position: 302
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---
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# entropy
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Calculates [Shannon entropy](https://en.wikipedia.org/wiki/Entropy_(information_theory)) of a column of values.
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**Syntax**
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``` sql
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entropy(val)
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```
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**Arguments**
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- `val` — Column of values of any type.
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**Returned value**
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- Shannon entropy.
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Type: [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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CREATE TABLE entropy (`vals` UInt32,`strings` String) ENGINE = Memory;
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INSERT INTO entropy VALUES (1, 'A'), (1, 'A'), (1,'A'), (1,'A'), (2,'B'), (2,'B'), (2,'C'), (2,'D');
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SELECT entropy(vals), entropy(strings) FROM entropy;
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```
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Result:
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``` text
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┌─entropy(vals)─┬─entropy(strings)─┐
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│ 1 │ 1.75 │
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└───────────────┴──────────────────┘
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```
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