## ATAN

The `ATAN` function in ES|QL is used to calculate the arctangent of a given numeric expression. The result is expressed in radians. If the input is null, the function will return null.

### Syntax

`ATAN(number)`

#### Parameters

- `number`: A numeric expression. If null, the function returns null.

### Examples

Here are a couple of examples of how you can use the `ATAN` function in ES|QL:

```esql
ROW a=12.9
| EVAL atan = ATAN(a)
```

In this example, the `ATAN` function is used to calculate the arctangent of the number 12.9.

```esql
ROW b=7.5
| EVAL atan_value = ATAN(b)
```

In this second example, the `ATAN` function is used to calculate the arctangent of the number 7.5. The result is stored in the `atan_value` variable.