Create list for Berquist-Sherman incremental severity model

g - Assumed loss emergence model, a function of the parameters a. Note g must be matrix-valued with size rows and size columns

berquist(B0, paid_to_date, upper_triangle_mask)

Arguments

B0	development triangle
paid_to_date	numeric vector of length size. It is the lower diagnal of the development triangle in row order. It represents the amount paid to date.
upper_triangle_mask	is a mask matrix of allowable data, upper triangular assuming same development increments as exposure increments

Details

g itself Basic design is for g to be a function of a single parameter vector, however in the simulations it is necessary to work on a matrix of parameters, one row for each simulated parameter, so g_obj must be flexible enough to handle both. Here g_obj is the Berquist-Sherman incremental severity model