The first derivative of the Ds-optimality criterion with respect to the model parameters. This is a sub-function of D_weight to run one iteration of Newton-Raphson method.
DD_weight_1(W, T, X, inv, inv1, order)
A numeric vector. The first K-1 weights for a given design
A numeric vector. Model parameter values for the 5PL model
A numeric vector. K dose levels for a given design
A numeric matrix. Inverse information matrix for the 5PL model
A numeric matrix. Inverse information matrix for the 4PL model
numeric. The number of model paraemters