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Building Model Formula

Source: R/mmrm.R
build_formula.Rd

This builds the model formula which is used inside fit_mmrm_j() and provided to mmrm::mmrm() internally. It can be instructive to look at the resulting formula directly sometimes. In particular, if a subgroup variable is included in vars, then the formula will include the interaction of subgroup with arm and visit.

Usage

build_formula(
  vars,
  cor_struct = c("unstructured", "toeplitz", "heterogeneous toeplitz", "ante-dependence",
    "heterogeneous ante-dependence", "auto-regressive", "heterogeneous auto-regressive",
    "compound symmetry", "heterogeneous compound symmetry")
)

Arguments

vars

(list)
variables to use in the model.

cor_struct

(string)
specify the covariance structure to use.

Value

Formula to use in mmrm::mmrm().

Examples

vars <- list(
  response = "AVAL",
  covariates = c("RACE", "SEX"),
  id = "USUBJID",
  arm = "ARMCD",
  visit = "AVISIT",
  subgroup = "REGION"
)
build_formula(vars, "auto-regressive")
#> AVAL ~ RACE + SEX + ARMCD * AVISIT * REGION + ar1(AVISIT | USUBJID)
#> <environment: 0x55c667421990>
build_formula(vars)
#> AVAL ~ RACE + SEX + ARMCD * AVISIT * REGION + us(AVISIT | USUBJID)
#> <environment: 0x55c655f49e08>