Set up an spatial simultaneous autoregressive (SAR) term in brms. The function does not evaluate its arguments -- it exists purely to help set up a model with SAR terms.
sar(M, type = "lag")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 of the SAR structure. Either "lag"
(for SAR of the response values) or "error"
(for SAR of the residuals). More information is
provided in the 'Details' section.
An object of class 'sar_term', which is a list
of arguments to be interpreted by the formula
parsing functions of brms.
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. Currently, only families
gaussian and student support SAR structures.
if (FALSE) {
data(oldcol, package = "spdep")
fit1 <- brm(CRIME ~ INC + HOVAL + sar(COL.nb, type = "lag"),
data = COL.OLD, data2 = list(COL.nb = COL.nb),
chains = 2, cores = 2)
summary(fit1)
plot(fit1)
fit2 <- brm(CRIME ~ INC + HOVAL + sar(COL.nb, type = "error"),
data = COL.OLD, data2 = list(COL.nb = COL.nb),
chains = 2, cores = 2)
summary(fit2)
plot(fit2)
}