mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-17 13:13:36 +00:00
44 lines
1.1 KiB
Markdown
44 lines
1.1 KiB
Markdown
|
---
|
||
|
|
toc_priority: 302
|
||
|
|
---
|
||
|
|
|
||
|
|
# entropy {#entropy}
|
||
|
|
|
||
|
|
Вычисляет [информационную энтропию](https://ru.wikipedia.org/wiki/%D0%98%D0%BD%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%BD%D0%B0%D1%8F_%D1%8D%D0%BD%D1%82%D1%80%D0%BE%D0%BF%D0%B8%D1%8F) столбца данных.
|
||
|
|
|
||
|
|
**Синтаксис**
|
||
|
|
|
||
|
|
``` sql
|
||
|
|
entropy(val)
|
||
|
|
```
|
||
|
|
|
||
|
|
**Аргументы**
|
||
|
|
|
||
|
|
- `val` — столбец значений любого типа
|
||
|
|
|
||
|
|
**Возвращаемое значение**
|
||
|
|
|
||
|
|
- Информационная энтропия.
|
||
|
|
|
||
|
|
Тип: [Float64](../../../sql-reference/data-types/float.md).
|
||
|
|
|
||
|
|
**Пример**
|
||
|
|
|
||
|
|
Запрос:
|
||
|
|
|
||
|
|
``` sql
|
||
|
|
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;
|
||
|
|
```
|
||
|
|
|
||
|
|
Результат:
|
||
|
|
|
||
|
|
``` text
|
||
|
|
┌─entropy(vals)─┬─entropy(strings)─┐
|
||
|
|
│ 1 │ 1.75 │
|
||
|
|
└───────────────┴──────────────────┘
|
||
|
|
```
|