getprior {dfcrm}

Calibrating prior DLT rates

Description

Returns a vector of initial guesses of toxicity probabilities associated the doses for a given model sensitivity (set of indifference intervals).

Usage

getprior(halfwidth, target, nu, nlevel, model = "empiric", intcpt = 3)

Arguments

halfwidth

The desired halfwidth of the indifference intervals.

target

The target DLT rate.

nu

The prior guess of MTD.

nlevel

The number of test doses.

model

A character string to specify the working model used in the method. The default model is “empiric”. A one-parameter logistic model is specified by “logistic”.

intcpt

The intercept of the working logistic model. The default is 3. If model=“empiric”, this argument will be ignored.

Details

getprior is an “inverse” function of crmsens which gives the indifference intervals for a given set of initial guesses.

Value

A vector of length nlevel is returned.

References

Cheung, Y. K. and Chappell, R. (2002). A simple technique to evaluate model sensitivity in the continual reassessment method. Biometrics 58:671-674.

Lee, S. M. and Cheung Y. K. (2009). Model calibration in the continual reassessment method. Clinical Trials 6, 227-238.

Cheung, Y. K. (2011). Dose Finding by the Continual Reassessment Method. New York: Chapman & Hall/CRC Press.

See Also

crmsens

Examples

target <- 0.25
delta <- 0.10
mtd0 <- 3

# initial DLT rates with indifference intervals [0.15, 0.35].
prior <- getprior(delta, target, mtd0, nlevel=6, model="logistic")