library(lavaan)
data(simple_mediation)
mod <-
"
m ~ a * x
y ~ b * m + x
ab := a * b
"
fit <- sem(mod, simple_mediation, fixed.x = FALSE)
parameterEstimates(fit)
mod_gp <-
"
m ~ c(a1, a2) * x
y ~ c(b1, b2) * m + x
a1b1 := a1 * b1
a2b2 := a2 * b2
ab_diff := a1b1 - a2b2
"
fit_gp <- sem(mod_gp, simple_mediation, fixed.x = FALSE, group = "city")
parameterEstimates(fit_gp)
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