Plot Bivariate Parameter Posteriors (Pairs Plot)

Creates a pairs plot showing bivariate relationships between parameters. Divergent transitions (if present) are highlighted to help identify problematic posterior regions.

Usage

plot_pairs(
  fit,
  pars = NULL,
  highlight_divergent = TRUE,
  n_pars = 5,
  alpha = 0.3
)

Arguments

fit

A ratiod_fit object.

pars

Character vector of parameter names. If NULL, selects main variance parameters.

highlight_divergent

Logical; highlight divergent transitions in red (default: TRUE).

n_pars

Maximum number of parameters (default: 5).

alpha

Point transparency (default: 0.3).

Value

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

Details

Pairs plots help identify:

• Strong correlations between parameters (potential non-identifiability)

• Multimodality

• Regions where divergences cluster (indicating problematic geometry)

See also

plot_divergences(), diagnostics()

Examples

# \donttest{
sim <- sim_ratiod(n = 100, family = ratiod_poisson_gamma(), seed = 1)
fit <- tratio(y_num | y_denom ~ x1 + (1 | group), data = sim$data,
              family = ratiod_poisson_gamma(),
              control = list(iter = 1000, chains = 2, seed = 1))
plot_pairs(fit, pars = c("beta_num[1]", "beta_num[2]", "sigma_re"))

# }