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51 lines
1.2 KiB
Markdown
51 lines
1.2 KiB
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/theilsu
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sidebar_position: 201
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---
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# theilsU
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The `theilsU` function calculates the [Theil's U uncertainty coefficient](https://en.wikipedia.org/wiki/Contingency_table#Uncertainty_coefficient), a value that measures the association between two columns in a table. Its values range from −1.0 (100% negative association, or perfect inversion) to +1.0 (100% positive association, or perfect agreement). A value of 0.0 indicates the absence of association.
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**Syntax**
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``` sql
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theilsU(column1, column2)
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```
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**Arguments**
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- `column1` and `column2` are the columns to be compared
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**Returned value**
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- a value between -1 and 1
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**Return type** is always [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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The following two columns being compared below have a small association with each other, so the value of `theilsU` is negative:
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``` sql
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SELECT
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theilsU(a ,b)
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FROM
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(
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SELECT
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number % 10 AS a,
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number % 4 AS b
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FROM
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numbers(150)
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);
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```
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Result:
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```response
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┌────────theilsU(a, b)─┐
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│ -0.30195720557678846 │
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└──────────────────────┘
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```
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