Add a new .coef argument to vcovFWB(). A function can be supplied to extract a vector of coefficients from the fitted model in each bootstrap iteration if the default (stats::coef()) doesn't return a numeric vector (e.g., for nnet::multinom() models). An error message is now thrown if .coef doesn't return a numeric vector.
Fixed a bug where the names of quantities produced by fwb() when statistic returns an unnamed vector were incorrect.
fwb() and vcovFWB() now take an additional argument, wtype, which specifies how the weights are drawn. The default, "exp" is still to draw weights from an $\text{Exp}(1)$ distribution but other options, namely "multinom" for multinomial integer weights (which reproduce boot::boot() results exactly), "poisson" for Poisson integer weights, and "mammen" for second-order accurate Mammen weights as recommended by Lihua Lei here. (#4)
New functions set_fwb_wtype() and get_fwb_wtype() allow one to set global defaults for the wtype argument of fwb() and vcovFWB()`.
Fixed bugs related to the index argument of various functions, including bugs when the estimated quantity is not given a name.
Some error messages may be clearer.