mcmc_draws: MCMC chain draws from a fit

In tulpa: Templated Unified Library for Posterior Approximation in Bayesian Hierarchical Models

MCMC chain draws from a fit

Description

Returns a fit's posterior draws only when they form a genuine MCMC chain (⁠$draws_kind == "chain"⁠, or an untagged legacy fit); for an i.i.d. / approximation fit (nested Laplace, VI, SMC, ...) it returns NULL, because chain diagnostics do not apply. This is the accessor diagnostics() gates on. For the provenance-agnostic posterior sample used by summaries, see posterior_sample().

Usage

mcmc_draws(fit)

Arguments

fit	A tulpa_fit (or subclass) carrying posterior ⁠$draws⁠.

Value

The chain draws matrix/array, or NULL for a non-chain fit.

See Also

posterior_sample(), diagnostics()

Examples

set.seed(1)
d <- data.frame(x = rnorm(60))
d$y <- rpois(60, exp(0.5 + 0.3 * d$x))
fit <- tulpa(y ~ x, data = d, family = "poisson", mode = "hmc",
             control = list(n_iter = 400L, warmup = 200L, n_chains = 2L,
                            seed = 1L))
dim(mcmc_draws(fit))

tulpa documentation built on Oct. 19, 2026, 5:09 p.m.