# preprocess.extend_to_mudline()

Prepend the unlogged feet between the mudline and the first logged foot.

Usage

[Source](https://github.com/lornearnold/driven-pile/blob/main/src/driven_pile/preprocess.py#L126-L149)

``` python
preprocess.extend_to_mudline(
    elevation,
    mudline,
)
```

## Parameters

`elevation: array_like`  
Logged elevations, ft, descending.

`mudline: float`  
Soil surface elevation, ft.

## Returns

`elevation: ndarray`  
Grid elevations, one-foot steps from `mudline - 1` down to the first logged foot, followed by the logged elevations.

`n_top: int`  
Number of prepended feet.