Constructs a character representation of the random effects formula
for fitting a MMRM for subject by visit in the format required for mmrm::mmrm()
.
Usage
random_effects_expr(
cov_struct = c("us", "ad", "adh", "ar1", "ar1h", "cs", "csh", "toep", "toeph"),
cov_by_group = FALSE
)
Arguments
- cov_struct
Character - The covariance structure to be used, must be one of "us"
(default),
"ad"
, "adh"
, "ar1"
, "ar1h"
, "cs"
, "csh"
, "toep"
, or "toeph"
)
- cov_by_group
Boolean - Whenever or not to use separate covariances per each group level
Details
For example assuming the user specified a covariance structure of "us" and that no groups
were provided this will return
If cov_by_group
is set to FALSE
then this indicates that separate covariance matrices
are required per group and as such the following will be returned:
us( visit | group / subjid )