strategies function

Strategies

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)

Arguments

• pars_group: A list of parameters for the subject's group. See details.
• pars_ref: A list of parameters for the subject's reference group. See details.
• index_mar: 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).

Details

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)