gistfile1.txt

# Load libraries
library(brms)
library(tidyverse)

# Load data

data <- read_csv("temp_data.csv")

# Define model
Model2_Language_f <- bf(Outcome ~ 0 + language + language:Diagnosis +
                          (1 | p | gr(ID, by=group)),
                        sigma ~ 0 + language + language:Diagnosis +
                          (1 | p | gr(ID, by=group))
)

# Define priors

PriorLS <- c(
  prior(normal(0, .01), class = sd),
  prior(normal(0, .05), class = b),
  prior(normal(0,.05), class=b, dpar = sigma),
  prior(normal(0,.01), class=sd, dpar = sigma),
  prior(lkj(5), class = cor)
)


InformedPriorLS <- c(
  prior(normal(0, 0.1), class = sd) ,
  prior(normal(0.38, 0.11), class = b),
  prior(normal(-0.17, 0.11), class = b, coef = languagedk),
  prior(normal(-0.17, 0.11), class = b, coef = languageus), #0.0763
  prior(normal(0, 0.05), class = b, dpar = sigma),
  prior(normal(0, 0.01), class = sd, dpar = sigma),
  prior(lkj(5), class = cor)
)

# Run model

m <- brm(Model2_Language_f,
         data = data,
         family = gaussian,
         prior = PriorLS,
         sample_prior = T
)

# No errors
m <- brm(Model2_Language_f,
         data = data,
         family = gaussian,
         prior = InformedPriorLS,
         sample_prior = T
)

# Error
#Error in parse(text = expr) : <text>:6:5: unexpected ')'
#5: b_sigma
#6: sd_1)