Set up an unstructured (UNSTR) correlation term in brms. The function does
not evaluate its arguments -- it exists purely to help set up a model with
UNSTR terms.
Usage
unstr(time, gr)
Value
An object of class 'unstr_term', which is a list
of arguments to be interpreted by the formula
parsing functions of brms.
Arguments
time
An optional time variable specifying the time ordering
of the observations. By default, the existing order of the observations
in the data is used.
gr
An optional grouping variable. If specified, the correlation
structure is assumed to apply only to observations within the same grouping
level.
if (FALSE) {
# add an unstructured correlation matrix for visits within the same patientfit <- brm(count ~ Trt + unstr(visit, patient), data = epilepsy)
summary(fit)
}