fitEnrollment {EventPredInCure} | R Documentation |
Fit enrollment model
Description
Fits a specified enrollment model to the enrollment data.
Usage
fitEnrollment(
df,
enroll_model = "b-spline",
nknots = 0,
accrualTime = 0,
criterion = "both"
)
Arguments
df |
The subject-level enrollment data, including |
enroll_model |
The enrollment model which can be specified as "Poisson", "Time-decay", "B-spline", or "Piecewise Poisson". By default, it is set to "B-spline". |
nknots |
The number of inner knots for the B-spline enrollment model. By default, it is set to 0. |
accrualTime |
The accrual time intervals for the piecewise Poisson model. Must start with 0, e.g., c(0, 30) breaks the time axis into 2 accrual intervals: [0, 30) and [30, Inf). By default, it is set to 0. |
criterion |
A character variable to denote the criterion in model
selection to shown in the figure, which can be set to one of the following
options: "aic","bic" or "both". By default,it is set to |
Details
For the time-decay model, the mean function is
mu(t) = mu/delta*(t - 1/delta*(1 - exp(-delta*t)))
and the rate function is
lambda(t) = mu/delta*(1 - exp(-delta*t))
.
For the B-spline model, the daily enrollment rate is approximated as
lambda(t) = exp(B(t)*theta)
,
where B(t)
represents the B-spline basis functions.
Value
A list of results from the model fit including key information
such as the enrollment model, model
, the estimated model
parameters, theta
, the covariance matrix, vtheta
, and
the Bayesian Information Criterion, bic
, and Akaike Information Criterion, aic
, as well as
the design matrix x
for the B-spline enrollment model, and
accrualTime
for the piecewise Poisson enrollment model.
The fitted enrollment curve is also returned.
References
Zhang, Xiaoxi, and Qi Long. "Stochastic modeling and prediction for accrual in clinical trials." Statistics in Medicine 29.6 (2010): 649-658.
Examples
enroll_fit <- fitEnrollment(df = interimData1, enroll_model = "b-spline",
nknots = 1)