smalldd1 function

Sub-function of the function D_weight_2

This computes the second derivative of the D-optimality criterion with respect to the model parameters for a specified model.

smalldd1(T, x1, x2, xl, inv, order)

Arguments

• T: A numeric vector. Model parameter values
• x1: A numeric. ith dose level
• x2: A numeric. jth dose level
• xl: A numeric. last dose level
• inv: A numeric matrix. Inverse information matrix
• order: numeric. The number of model paraemters: 3, 4, 5 for the 3, 4, 5PL models respectively