Add bootstrapped confidence intervals

This function is meant to be run after `sm_predict` or `sm_regression` and will calculate bootstrapped confidence intervals for `sm_predict` objects and add the bootstraped model estimates for `sm_regression` objects.

add_ci(x, ...)

Arguments

x	`sm_predict` or `sm_regression` object
...	further arguments passed to or from other methods.

See also

add_ci.sm_regression