---
title: map() function
description: map() iterates over and applies a function to input rows.
url: https://docs.influxdata.com/flux/v0/stdlib/universe/map/
estimated_tokens: 2641
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/universe/map/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.7.0+

InfluxDB support

`map()` iterates over and applies a function to input rows.

Each input row is passed to the `fn` as a record, `r`.
Each `r` property represents a column key-value pair.
Output values must be of the following supported column types:

* float
* integer
* unsigned integer
* string
* boolean
* time

### Output data

Output tables are the result of applying the map function (`fn`) to each
record of the input tables. Output records are assigned to new tables based
on the group key of the input stream.
If the output record contains a different value for a group key column, the
record is regrouped into the appropriate table.
If the output record drops a group key column, that column is removed from
the group key.

#### Preserve columns

`map()` drops any columns that are not mapped explicitly by column label or
implicitly using the `with` operator in the `fn` function.
The `with` operator updates a record property if it already exists, creates
a new record property if it doesn’t exist, and includes all existing
properties in the output record.

```no_run
data
    |> map(fn: (r) => ({ r with newColumn: r._value * 2 }))
```

##### Function type signature

```js
(<-tables: stream[A], fn: (r: A) => B, ?mergeKey: bool) => stream[B]
```

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

## Parameters

### fn

(Required)
Single argument function to apply to each record.
The return value must be a record.

### mergeKey

*(Deprecated)* Merge group keys of mapped records. Default is `false`.

### tables

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

## Examples

* [Square the value in each row](#square-the-value-in-each-row)
* [Create a new table with new columns](#create-a-new-table-with-new-columns)
* [Add new columns and preserve existing columns](#add-new-columns-and-preserve-existing-columns)

### Square the value in each row

```js
import "sampledata"

sampledata.int()
    |> map(fn: (r) => ({r with _value: r._value * r._value}))
```

[](#view-example-input-and-output)

View example input and output

#### 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|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|   4   | t1  |
|2021-01-01T00:00:10Z|  100  | t1  |
|2021-01-01T00:00:20Z|  49   | t1  |
|2021-01-01T00:00:30Z|  289  | t1  |
|2021-01-01T00:00:40Z|  225  | t1  |
|2021-01-01T00:00:50Z|  16   | t1  |

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  361  | t2  |
|2021-01-01T00:00:10Z|  16   | t2  |
|2021-01-01T00:00:20Z|   9   | t2  |
|2021-01-01T00:00:30Z|  361  | t2  |
|2021-01-01T00:00:40Z|  169  | t2  |
|2021-01-01T00:00:50Z|   1   | t2  |

### Create a new table with new columns

```js
import "sampledata"

sampledata.int()
    |> map(
        fn: (r) => ({time: r._time, source: r.tag, alert: if r._value > 10 then true else false}),
    )
```

[](#view-example-input-and-output)

View example input and output

#### 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        |source|alert|
|--------------------|------|-----|
|2021-01-01T00:00:00Z|  t1  |false|
|2021-01-01T00:00:10Z|  t1  |false|
|2021-01-01T00:00:20Z|  t1  |false|
|2021-01-01T00:00:30Z|  t1  |true |
|2021-01-01T00:00:40Z|  t1  |true |
|2021-01-01T00:00:50Z|  t1  |false|
|2021-01-01T00:00:00Z|  t2  |true |
|2021-01-01T00:00:10Z|  t2  |false|
|2021-01-01T00:00:20Z|  t2  |false|
|2021-01-01T00:00:30Z|  t2  |true |
|2021-01-01T00:00:40Z|  t2  |true |
|2021-01-01T00:00:50Z|  t2  |false|

### Add new columns and preserve existing columns

Use the `with` operator on the `r` record to preserve columns not directly
operated on by the map operation.

```js
import "sampledata"

sampledata.int()
    |> map(fn: (r) => ({r with server: "server-${r.tag}", valueFloat: float(v: r._value)}))
```

[](#view-example-input-and-output)

View example input and output

#### 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| server  |\*tag|valueFloat|
|--------------------|-------|---------|-----|----------|
|2021-01-01T00:00:00Z|  \-2  |server-t1| t1  |   \-2    |
|2021-01-01T00:00:10Z|  10   |server-t1| t1  |    10    |
|2021-01-01T00:00:20Z|   7   |server-t1| t1  |    7     |
|2021-01-01T00:00:30Z|  17   |server-t1| t1  |    17    |
|2021-01-01T00:00:40Z|  15   |server-t1| t1  |    15    |
|2021-01-01T00:00:50Z|   4   |server-t1| t1  |    4     |

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

#### Related

* [Query using conditional logic](/influxdb/v2/query-data/flux/conditional-logic/)
* [Transform data with mathematic operations](/influxdb/v2/query-data/flux/mathematic-operations/)

[transformations](/flux/v0/tags/transformations/)
| _time | _value | *tag |
| --- | --- | --- |
| _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 |
| --- | --- | --- |
| _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 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 4 | t1 |
| 2021-01-01T00:00:10Z | 100 | t1 |
| 2021-01-01T00:00:20Z | 49 | t1 |
| 2021-01-01T00:00:30Z | 289 | t1 |
| 2021-01-01T00:00:40Z | 225 | t1 |
| 2021-01-01T00:00:50Z | 16 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 361 | t2 |
| 2021-01-01T00:00:10Z | 16 | t2 |
| 2021-01-01T00:00:20Z | 9 | t2 |
| 2021-01-01T00:00:30Z | 361 | t2 |
| 2021-01-01T00:00:40Z | 169 | t2 |
| 2021-01-01T00:00:50Z | 1 | t2 |

| _time | _value | *tag |
| --- | --- | --- |
| _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 |
| --- | --- | --- |
| _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 |

| time | source | alert |
| --- | --- | --- |
| time | source | alert |
| 2021-01-01T00:00:00Z | t1 | false |
| 2021-01-01T00:00:10Z | t1 | false |
| 2021-01-01T00:00:20Z | t1 | false |
| 2021-01-01T00:00:30Z | t1 | true |
| 2021-01-01T00:00:40Z | t1 | true |
| 2021-01-01T00:00:50Z | t1 | false |
| 2021-01-01T00:00:00Z | t2 | true |
| 2021-01-01T00:00:10Z | t2 | false |
| 2021-01-01T00:00:20Z | t2 | false |
| 2021-01-01T00:00:30Z | t2 | true |
| 2021-01-01T00:00:40Z | t2 | true |
| 2021-01-01T00:00:50Z | t2 | false |

| _time | _value | *tag |
| --- | --- | --- |
| _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 |
| --- | --- | --- |
| _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 |

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

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