---
title: math.dim() function
description: >
  `math.dim()` returns the maximum of `x - y` or `0`.
menu:
  flux_v0_ref:
    name: math.dim
    parent: math
    identifier: math/dim
weight: 101
---

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`math.dim()` returns the maximum of `x - y` or `0`.



##### Function type signature

```js
(x: float, y: float) => float
```

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

### x
({{< req >}})
x-value to use in the operation.



### y
({{< req >}})
y-value to use in the operation.




## Examples

- [Return the maximum difference between two values](#return-the-maximum-difference-between-two-values)
- [Use math.dim in map](#use-mathdim-in-map)

### Return the maximum difference between two values

```js
import "math"

math.dim(x: 12.2, y: 8.1)// 4.1


```


### Use math.dim in map

```js
import "math"

data
    |> map(fn: (r) => ({_time: r._time, _value: math.dim(x: r.x, y: r.y)}))

```

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#### Input data

| _time                | x   | y   |
| -------------------- | --- | --- |
| 2021-01-01T00:00:00Z | 3.9 | 1.2 |
| 2021-01-01T01:00:00Z | 4.2 | 2.4 |
| 2021-01-01T02:00:00Z | 5.3 | 3.6 |
| 2021-01-01T03:00:00Z | 6.8 | 4.8 |
| 2021-01-01T04:00:00Z | 7.5 | 5.1 |


#### Output data

| _time                | _value             |
| -------------------- | ------------------ |
| 2021-01-01T00:00:00Z | 2.7                |
| 2021-01-01T01:00:00Z | 1.8000000000000003 |
| 2021-01-01T02:00:00Z | 1.6999999999999997 |
| 2021-01-01T03:00:00Z | 2                  |
| 2021-01-01T04:00:00Z | 2.4000000000000004 |

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