---
title: stddev() function
description: >
  `stddev()` returns the standard deviation of non-null values in a specified column.
menu:
  flux_v0_ref:
    name: stddev
    parent: universe
    identifier: universe/stddev
weight: 101
flux/v0/tags: [transformations, aggregates]
introduced: 0.7.0
---

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`stddev()` returns the standard deviation of non-null values in a specified column.



##### Function type signature

```js
(<-tables: stream[A], ?column: string, ?mode: string) => stream[B] where A: Record, B: Record
```

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For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
{{% /caption %}}

## Parameters

### column

Column to operate on. Default is `_value`.



### mode

Standard deviation mode or type of standard deviation to calculate.
Default is `sample`.

**Available modes:**
- **sample**: Calculate the sample standard deviation where the data is
considered part of a larger population.
- **population**: Calculate the population standard deviation where the
data is considered a population of its own.

### tables

Input data. Default is piped-forward data (`<-`).




## Examples

### Return the standard deviation of values in each table

```js
import "sampledata"

sampledata.int()
    |> stddev()

```

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#### Input data

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z | -2      | t1   |
| 2021-01-01T00:00:10Z | 10      | t1   |
| 2021-01-01T00:00:20Z | 7       | t1   |
| 2021-01-01T00:00:30Z | 17      | t1   |
| 2021-01-01T00:00:40Z | 15      | t1   |
| 2021-01-01T00:00:50Z | 4       | t1   |

| _time                | _value  | *tag |
| -------------------- | ------- | ---- |
| 2021-01-01T00:00:00Z | 19      | t2   |
| 2021-01-01T00:00:10Z | 4       | t2   |
| 2021-01-01T00:00:20Z | -3      | t2   |
| 2021-01-01T00:00:30Z | 19      | t2   |
| 2021-01-01T00:00:40Z | 13      | t2   |
| 2021-01-01T00:00:50Z | 1       | t2   |


#### Output data

| *tag | _value            |
| ---- | ----------------- |
| t1   | 7.063993204979744 |

| *tag | _value            |
| ---- | ----------------- |
| t2   | 9.474527252938094 |

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