mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-15 19:02:04 +00:00
80 lines
1.9 KiB
Markdown
80 lines
1.9 KiB
Markdown
---
|
|
slug: /en/sql-reference/aggregate-functions/reference/cramersv
|
|
sidebar_position: 127
|
|
---
|
|
|
|
# cramersV
|
|
|
|
[Cramer's V](https://en.wikipedia.org/wiki/Cram%C3%A9r%27s_V) (sometimes referred to as Cramer's phi) is a measure of association between two columns in a table. The result of the `cramersV` function ranges from 0 (corresponding to no association between the variables) to 1 and can reach 1 only when each value is completely determined by the other. It may be viewed as the association between two variables as a percentage of their maximum possible variation.
|
|
|
|
:::note
|
|
For a bias corrected version of Cramer's V see: [cramersVBiasCorrected](./cramersvbiascorrected.md)
|
|
:::
|
|
|
|
**Syntax**
|
|
|
|
``` sql
|
|
cramersV(column1, column2)
|
|
```
|
|
|
|
**Parameters**
|
|
|
|
- `column1`: first column to be compared.
|
|
- `column2`: second column to be compared.
|
|
|
|
**Returned value**
|
|
|
|
- a value between 0 (corresponding to no association between the columns' values) to 1 (complete association).
|
|
|
|
Type: always [Float64](../../../sql-reference/data-types/float.md).
|
|
|
|
**Example**
|
|
|
|
The following two columns being compared below have no association with each other, so the result of `cramersV` is 0:
|
|
|
|
Query:
|
|
|
|
``` sql
|
|
SELECT
|
|
cramersV(a, b)
|
|
FROM
|
|
(
|
|
SELECT
|
|
number % 3 AS a,
|
|
number % 5 AS b
|
|
FROM
|
|
numbers(150)
|
|
);
|
|
```
|
|
|
|
Result:
|
|
|
|
```response
|
|
┌─cramersV(a, b)─┐
|
|
│ 0 │
|
|
└────────────────┘
|
|
```
|
|
|
|
The following two columns below have a fairly close association, so the result of `cramersV` is a high value:
|
|
|
|
```sql
|
|
SELECT
|
|
cramersV(a, b)
|
|
FROM
|
|
(
|
|
SELECT
|
|
number % 10 AS a,
|
|
number % 5 AS b
|
|
FROM
|
|
numbers(150)
|
|
);
|
|
```
|
|
|
|
Result:
|
|
|
|
```response
|
|
┌─────cramersV(a, b)─┐
|
|
│ 0.8944271909999159 │
|
|
└────────────────────┘
|
|
```
|