The $grad_log_prob() method provides access to the Stan model's log_prob function and its derivative.

grad_log_prob(unconstrained_variables, jacobian_adjustment = TRUE)

Arguments

unconstrained_variables

(numeric) A vector of unconstrained parameters to be passed to grad_log_prob.

jacobian_adjustment

(logical) Whether to include the log-density adjustments from un/constraining variables.

Examples

# \dontrun{
fit_mcmc <- cmdstanr_example("logistic", method = "sample", force_recompile = TRUE)
#> Compiling Stan program...
fit_mcmc$init_model_methods()
#> Compiling additional model methods...
fit_mcmc$grad_log_prob(unconstrained_variables = c(0.5, 1.2, 1.1, 2.2))
#> [1]   1.462151 -26.619534 -25.528776 -14.286822
#> attr(,"log_prob")
#> [1] -130.2141
# }