cor_ar {brms}  R Documentation 
This function is deprecated. Please see ar
for the new syntax.
This function is a constructor for the cor_arma
class,
allowing for autoregression terms only.
cor_ar(formula = ~1, p = 1, cov = FALSE)
formula 
A one sided formula of the form 
p 
A nonnegative integer specifying the autoregressive (AR) order of the ARMA structure. Default is 1. 
cov 
A flag indicating whether ARMA effects should be estimated by
means of residual covariance matrices. This is currently only possible for
stationary ARMA effects of order 1. If the model family does not have
natural residuals, latent residuals are added automatically. If

AR refers to autoregressive effects of residuals, which is what is typically understood as autoregressive effects. However, one may also model autoregressive effects of the response variable, which is called ARR in brms.
An object of class cor_arma
containing solely autoregression terms.
cor_ar(~visitpatient, p = 2)