Plot Effective Sample Size Diagnostic

Creates a visual display of effective sample size (ESS) for all parameters, expressed as a ratio of ESS to total samples. Low ESS indicates high autocorrelation.

Usage

plot_ess(fit, type = c("bulk", "tail"), threshold = 400, pars = NULL)

Arguments

fit: A tulpa_fit object.
type: Type of ESS: "bulk" (default) or "tail".
threshold: Minimum acceptable ESS (default: 400).
pars: Character vector of parameter names to include.

Value

A ggplot object (if ggplot2 available) or base R plot (invisible).

Details

ESS/iter ratio interpretation:

Green: ESS >= threshold
Yellow: threshold/2 <= ESS < threshold
Red: ESS < threshold/2

Examples

# \donttest{
set.seed(123)
df <- data.frame(x = rnorm(60))
df$y <- rpois(60, exp(0.5 + 0.3 * df$x))
fit <- tulpa(y ~ x, data = df, family = "poisson", mode = "hmc",
             control = list(n_iter = 500L, warmup = 250L, n_chains = 2L,
                            seed = 1L))
plot_ess(fit)
plot_ess(fit, type = "tail")
# }