a table of (estimated) marginal likelihoods,
as, for example, created by est_marg_liks.
This data.frame has the following columns:
site_model_name: name of the site model,
must be an element of get_site_model_names
clock_model_name: name of the clock model,
must be an element of get_clock_model_names
tree_prior_name: name of the tree prior,
must be an element of get_tree_prior_names
marg_log_lik: estimated marginal (natural) log likelihood
marg_log_lik_sd: estimated error of marg_log_lik
weight: relative model weight, a value from 1.0 (all
evidence is in favor of this model combination) to 0.0 (no
evidence in favor of this model combination)
ess: effective sample size of the marginal likelihood
estimation