R: Set up basic grouping terms in 'brms'

gr {brms} | R Documentation

## Set up basic grouping terms in brms

### Description

Function used to set up a basic grouping term in brms. The function does not evaluate its arguments – it exists purely to help set up a model with grouping terms. `gr` is called implicitly inside the package and there is usually no need to call it directly.

### Usage

    gr(..., by = NULL, dist = "gaussian")

### Arguments

`...` | One or more terms containing grouping factors.
`by` | An optional factor variable, specifying sub-populations of the groups. For each level of the `by` variable, a separate variance-covariance matrix will be fitted. Levels of the grouping factor must be nested in levels of the `by` variable.
`dist` | Name of the distribution of the group-level effects. Currently `"gaussian"` is the only option.

### See Also

`brmsformula`

### Examples

    ## Not run:
    # model using basic lme4-style formula
    fit1 <- brm(count ~ Trt + (1|patient), data = epilepsy)
    summary(fit1)

    # equivalent model using 'gr' which is called anyway internally
    fit2 <- brm(count ~ Trt + (1|gr(patient)), data = epilepsy)
    summary(fit2)

    # include Trt as a by variable
    fit3 <- brm(count ~ Trt + (1|gr(patient, by = Trt)), data = epilepsy)
    summary(fit3)

    ## End(Not run)

[Package brms version 2.6.0 Index]