---
title: kaufmansER() function
description: >
  `kaufmansER()` computes the Kaufman's Efficiency Ratio (KER) of values in the
  `_value` column for each input table.
menu:
  flux_v0_ref:
    name: kaufmansER
    parent: universe
    identifier: universe/kaufmansER
weight: 101
flux/v0/tags: [transformations]
introduced: 0.40.0
---

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`kaufmansER()` computes the Kaufman's Efficiency Ratio (KER) of values in the
`_value` column for each input table.

Kaufman’s Efficiency Ratio indicator divides the absolute value of the Chande
Momentum Oscillator by 100 to return a value between 0 and 1.
Higher values represent a more efficient or trending market.

##### Function type signature

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

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

### n
({{< req >}})
Period or number of points to use in the calculation.



### tables

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




## Examples

### Compute the Kaufman's Efficiency Ratio

```js
import "sampledata"

sampledata.int()
    |> kaufmansER(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 |
| -------------------- | ------------------- | ---- |
| 2021-01-01T00:00:30Z | 0.76                | t1   |
| 2021-01-01T00:00:40Z | 0.33333333333333337 | t1   |
| 2021-01-01T00:00:50Z | 0.13043478260869565 | t1   |

| _time                | _value             | *tag |
| -------------------- | ------------------ | ---- |
| 2021-01-01T00:00:30Z | 0                  | t2   |
| 2021-01-01T00:00:40Z | 0.2571428571428572 | t2   |
| 2021-01-01T00:00:50Z | 0.1                | t2   |

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