Including offsets is another option to integrate spatial prior information in linear and additive regression models. Offsets shift the intercept of the regression fit by a certain amount. Although only one offset can be added to a regression model, it is possible to combine several spatial-explicit estimates into one offset by calculating the sum of all spatial-explicit layers.

## Usage

```
add_offset(x, layer, add = TRUE)
# S4 method for BiodiversityDistribution,SpatRaster
add_offset(x, layer, add = TRUE)
# S4 method for BiodiversityDistribution,sf
add_offset(x, layer, add = TRUE)
```

## Arguments

- x
`distribution()`

(i.e.`BiodiversityDistribution`

) object.- layer
A

`sf`

or`SpatRaster`

object with the range for the target feature.- add
`logical`

specifying whether new offset is to be added. Setting this parameter to`FALSE`

replaces the current offsets with the new one (Default:`TRUE`

).

## Value

Adds an offset to a `distribution`

object.

## Details

This function allows to set any specific offset to a regression
model. The offset has to be provided as spatial `SpatRaster`

object. This
function simply adds the layer to a `distribution()`

object.
**Note that any transformation of the offset (such as log) has do be done externally!**

If the layer is range and requires additional formatting, consider using the
function `add_offset_range()`

which has additional functionalities such
such distance transformations.

## Note

Since offsets only make sense for linear regressions (and not for instance regression tree based methods such as engine_bart), they do not work for all engines. Offsets specified for non-supported engines are ignored during the estimation

## References

Merow, C., Allen, J.M., Aiello-Lammens, M., Silander, J.A., 2016. Improving niche and range estimates with Maxent and point process models by integrating spatially explicit information. Glob. Ecol. Biogeogr. 25, 1022–1036. https://doi.org/10.1111/geb.12453

## See also

Other offset:
`add_offset_bias()`

,
`add_offset_elevation()`

,
`add_offset_range()`

,
`rm_offset()`

## Examples

```
if (FALSE) {
x <- distribution(background) |>
add_predictors(covariates) |>
add_offset(nicheEstimate)
}
```