These functions are used to implement various reference based imputation strategies by combining a subjects own distribution with that of a reference distribution based upon which of their visits failed to meet the Missing-at-Random (MAR) assumption.
strategy_MAR(pars_group, pars_ref, index_mar)strategy_JR(pars_group, pars_ref, index_mar)
strategy_CR(pars_group, pars_ref, index_mar)
strategy_CIR(pars_group, pars_ref, index_mar)
strategy_LMCF(pars_group, pars_ref, index_mar)
A list of parameters for the subject's group. See details.
A list of parameters for the subject's reference group. See details.
A logical vector indicating which visits meet the MAR assumption for the subject. I.e. this identifies the observations after a non-MAR intercurrent event (ICE).
pars_group and pars_ref both must be a list containing elements mu and sigma.
mu must be a numeric vector and sigma must be a square matrix symmetric covariance
matrix with dimensions equal to the length of mu and index_mar. e.g.
list(
mu = c(1,2,3),
sigma = matrix(c(4,3,2,3,5,4,2,4,6), nrow = 3, ncol = 3)
)
Users can define their own strategy functions and include them via the strategies
argument to impute() using getStrategies(). That being said the following
strategies are available "out the box":
Missing at Random (MAR)
Jump to Reference (JR)
Copy Reference (CR)
Copy Increments in Reference (CIR)
Last Mean Carried Forward (LMCF)