Return the data frame containing the gradients for all parameters.
Examples
# \dontrun{
test <- cmdstanr_example("logistic", method = "diagnose")
# retrieve the gradients
test$gradients()
#> param_idx value model finite_diff error
#> 1 0 0.777333 -3.95076 -3.95076 1.93379e-09
#> 2 1 -0.327811 -10.01080 -10.01080 -4.28308e-09
#> 3 2 1.407420 -26.81840 -26.81840 1.50014e-09
#> 4 3 -1.260890 24.28000 24.28000 1.44433e-09
# }