# cor_sar

##### Spatial simultaneous autoregressive (SAR) structures

These functions are constructors for the `cor_sar`

class
implementing spatial simultaneous autoregressive structures.
The `lagsar`

structure implements SAR of the response values:
$$y = \rho W y + \eta + e$$
The `errorsar`

structure implements SAR of the residuals:
$$y = \eta + u, u = \rho W u + e$$
In the above equations, \(\eta\) is the predictor term and
\(e\) are independent normally or t-distributed residuals.

##### Usage

`cor_sar(W, type = c("lag", "error"))`cor_lagsar(W)

cor_errorsar(W)

##### Arguments

- W
An object specifying the spatial weighting matrix. Can be either the spatial weight matrix itself or an object of class

`listw`

or`nb`

, from which the spatial weighting matrix can be computed.- type
Type of the SAR structure. Either

`"lag"`

(for SAR of the response values) or`"error"`

(for SAR of the residuals).

##### Details

Currently, only families `gaussian`

and `student`

support SAR structures.

##### Value

An object of class `cor_sar`

to be used in calls to
`brm`

.

##### Examples

```
# NOT RUN {
data(oldcol, package = "spdep")
fit1 <- brm(CRIME ~ INC + HOVAL, data = COL.OLD,
autocor = cor_lagsar(COL.nb),
chains = 2, cores = 2)
summary(fit1)
plot(fit1)
fit2 <- brm(CRIME ~ INC + HOVAL, data = COL.OLD,
autocor = cor_errorsar(COL.nb),
chains = 2, cores = 2)
summary(fit2)
plot(fit2)
# }
# NOT RUN {
# }
```

*Documentation reproduced from package brms, version 2.4.0, License: GPL (>= 3)*