This function computes each element of the vector function c_weight_1 which is the first derivative of the c-optimality criterion with respect to the model parameters.
D1(T, x, xl, inv, p, order)
A numeric vector. Model parameter values
A numeric. ith 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