---
title: doubleEMA() function
description: >
  `doubleEMA()` returns the double exponential moving average (DEMA) of values in
  the `_value` column grouped into `n` number of points, giving more weight to
  recent data.
menu:
  flux_v0_ref:
    name: doubleEMA
    parent: universe
    identifier: universe/doubleEMA
weight: 101
flux/v0/tags: [transformations]
introduced: 0.38.0
---

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`doubleEMA()` returns the double exponential moving average (DEMA) of values in
the `_value` column grouped into `n` number of points, giving more weight to
recent data.

#### Double exponential moving average rules
- A double exponential moving average is defined as `doubleEMA = 2 * EMA_N - EMA of EMA_N`.
    - `EMA` is an exponential moving average.
    - `N = n` is the period used to calculate the `EMA`.
- A true double exponential moving average requires at least `2 * n - 1` values.
  If not enough values exist to calculate the double `EMA`, it returns a `NaN` value.
- `doubleEMA()` inherits all `exponentialMovingAverage()` rules.

##### Function type signature

```js
(<-tables: stream[{A with _value: B}], n: int) => stream[C] where B: Numeric, C: Record
```

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For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
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## Parameters

### n
({{< req >}})
Number of points to average.



### tables

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




## Examples

### Calculate a three point double exponential moving average

```js
import "sampledata"

sampledata.int()
    |> doubleEMA(n: 3)

```

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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

| _time                | _value             | *tag |
| -------------------- | ------------------ | ---- |
| 2021-01-01T00:00:40Z | 16.333333333333336 | t1   |
| 2021-01-01T00:00:50Z | 7.916666666666668  | t1   |

| _time                | _value             | *tag |
| -------------------- | ------------------ | ---- |
| 2021-01-01T00:00:40Z | 15.027777777777779 | t2   |
| 2021-01-01T00:00:50Z | 5.034722222222221  | t2   |

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