VNM (version 4.1)

S.Weight: Identify optimal weights for given dose levels.

Description

Identify optimal weights that maximize the efficiency for estimating 3 objectives (model parameters, the ED50, the MED) for given dose levels under the 4-parameter logistic model. The weights represent the proportional allocations of subjects to given dose levels.

Usage

S.Weight(X,P,lambda,delta,epsilon_w)

Arguments

X

A numeric vector. Given dose levels to search the optimal weights.

P

A numeric vector. Solicited information on nominal values for the vector. P=(p1, p2, p3, p4), where p1 is the lower limit of the response, p2 is Emax, p3 is the ED50 and p4 is the slope at the ED50.

lambda

A numeric vector. User select weights. lambda=c(q1, q2), where q1,q2 represent weights for estimating model parameter and estimating the ED50 respectively. They are non-negative and q1+q2<=1.

delta

Numeric. Predetermined clinically significant effect to define the MED. The MED is the dose producing the mean response of dt units better than the minimum dose.

epsilon_w

Numeric. Stopping criterion for the Newton Raphson method to search the optimal weights for the given dose levels. Default is 10^-6.

Value

An object of class SW.

References

Seung Won Hyun, Weng Kee Wong, and Yarong Yang (2014), VNM: An R Package for Finding Multiple-Objective Optimal Designs for the 4-Parameter Logistic Model, submitted to Journal of Statistical Software.

Seung Won Hyun and Weng Kee Wong (2015), Multiple Objective Optimal Designs to Study the Interesting Features in a Dose-Response Relationship, accepted by the International Journal of Biostatistics.

Examples

   S.Weight(X=c(-6.91, 2.22, 3.75, 4.60),P=c(22,16.8,70,1),lambda=c(1/3,1/3),delta=5)