dfcrm (version 0.1-2)

cohere: Coherence of two-stage CRM

Description

Returns a message on the coherence status of a two-stage CRM design.

Usage

cohere(prior, target, x0, method = "bayes", model = "empiric", 
    intcpt = 3, scale = sqrt(1.34), detail = TRUE)

Arguments

prior

A vector of initial guesses of toxicity probabilities associated the doses.

target

The target DLT rate.

x0

The initial design containing a non-decreasing sequence of dose levels. The length of the initial design is the sample size.

method

A character string to specify the method for parameter estimation. The default method ``bayes'' estimates the model parameter by the posterior mean. Maximum likelihood estimation is specified by ``mle''.

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.

scale

Standard deviation of the normal prior of the model parameter. Default is sqrt(1.34).

detail

If TRUE, details about incoherent escalations will be displayed.

Value

• message
  A string character giving a message regarding the coherence status of a two-stage CRM design.

References

Cheung, Y. K. (2005). Coherence principles in dose-finding studies. Biometrika 92:863-873.

See Also

crm

Examples

prior <- c(0.05,0.10,0.20,0.35,0.50,0.70)
x0 <- c(rep(1,3),rep(2,3),rep(3,3),rep(4,3),rep(5,3),rep(6,9))

# The above design is coherent when target rate = 0.20
foo <- cohere(prior,target=0.2,x0)
foo

# The design is incoherent if a larger target DLT rate is used.
foo2 <- cohere(prior,target=0.3,x0)