brms (version 2.1.0)

mm: Set up multi-membership grouping terms in brms

Description

Function to set up a multi-membership grouping term in brms. The function does not evaluate its arguments -- it exists purely to help set up a model with grouping terms.

Usage

mm(..., weights = NULL, scale = TRUE)

Arguments

...

One or more terms containing grouping factors.

weights

A matrix specifying the weights of each member. It should have as many columns as grouping terms specified in .... If NULL (the default), equally weights are used.

scale

Logical; if TRUE (the default), weights are standardized in order to sum to one per row. If negative weights are specified, scale needs to be set to FALSE.

See Also

brmsformula

Examples

# NOT RUN {
# simulate some data
dat <- data.frame(y = rnorm(100), x = rnorm(100), 
                  g1 = sample(1:10, 100, TRUE),
                  g2 = sample(1:10, 100, TRUE))
# multi-membership model with two members per group and equal weights
fit1 <- brm(y ~ x + (1|mm(g1, g2)), data = dat)
summary(fit1)

# weight the first member two times for than the second member
dat$w1 <- rep(2, 100)
dat$w2 <- rep(1, 100)
fit2 <- brm(y ~ x + (1|mm(g1, g2, weights = cbind(w1, w2))), data = dat)
summary(fit2)
# }
# NOT RUN {
  
# }