D_weight: One iteration to run Newton Raphson to get D-optimal weights
In Opt5PL: Optimal Designs for the 5-Parameter Logistic Model

This is a sub-part of running Newton Raphon method to search D-optimal weights for the given design points. This is function probvides the obtained D-optimal weights after one iteration of Newton Raphson method.

1	D_weight(W, T, X, d, q)

`W`	A numeric vector. The first K-1 weights for a given design
`T`	A numeric vector. Model parameter values
`X`	A numeric vector. K dose levels for a given design
`d`	Numeric. Step adjustment
`q`	A numeric vector. User select weights defined in the function RDOPT