This function computes each element of the matrix function c_weight_2 which is the second derivative of the c-optimality criterion with respect to the model parameters.
DD1(T, x1, x2, xl, inv, p, order)
A numeric vector. Model parameter values
A numeric. ith dose level for a given design
A numeric. jth dose level for a given design
A numeric. last dose level for a given design
A numeric matrix. Inverse of the information matrix
A numeric. Define EDp
numeric. The number of model paraemters