getinit {dfcrm} | R Documentation |
Returns an initial design that is compatible with the specified CRM setup when used in a two-stage design.
getinit(prior, target, n, nK = round(n/3), method = "bayes", model = "empiric", intcpt = 3, scale = sqrt(1.34), detail = FALSE)
prior |
A vector of initial guesses of toxicity probabilities associated the doses. |
target |
The target DLT rate. |
n |
The sample size of the trial. |
nK |
The minimum number of subjects required at the highest test dose in case of no toxicity throughout the trial. |
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, intermediate designs will be displayed. |
An initial design will be incompatible to the CRM setup if the
escalation pace is too conservative, i.e. slow. The algorithm in
getinit
starts the search of a compatible design with an
aggressive initial design that starts a trial at the second highest
dose. A more conservative design will be subsequently tested for
compatibility if the current design is compatible. The sequence
returned may be viewed as a conservative compatible initial design.
A non-decreasing sequence of dose levels is returned.
Cheung, Y. K. (2005). Coherence principles in dose-finding studies. Biometrika 92:863-873.
prior <- c(0.05,0.10,0.20,0.35,0.50,0.70) target <- 0.2 # Seach stops because it requires at least 8 subjects at the highest dose getinit(prior,target,25,nK=8,method="mle",detail=TRUE) # Search stops because an incompatible design is reached getinit(prior,0.3,25,nK=8,method="mle",detail=TRUE)