I analyzed a 46 dichotomous items matrix using the Bayesian 1PL (brms R package). Here is the synthax I used:
formula_va_1pl <- bf(Xb16 ~ 1 + (1 | It16) + (1 | P16)) prior_va_1pl <- prior("normal(0, 3)", class = "sd", group = "It16") + prior("normal(0, 3)", class = "sd", group = "P16") fit_va_1pl <- brm(formula = formula_va_1pl, data = X16, family = brmsfamily("bernoulli","logit"), prior = prior_va_1pl)
I wish to extract the MCMC chains of every items under investigation. I find that posterior_samples function need to be used here. For example:
samples <- posterior_samples(fit_va_1pl,)
Nevertheless, I don’t understand clearly what is the specific MCMC chain values for the first chain regarding difficulty of item 4 for example.
Thanking you VERY MUCH in advance…