as.cov_struct {mmrm} | R Documentation |
Coerce into a Covariance Structure Definition
Description
Usage
as.cov_struct(x, ...)
## S3 method for class 'formula'
as.cov_struct(x, warn_partial = TRUE, ...)
Arguments
x |
an object from which to derive a covariance structure. See object specific sections for details. |
... |
additional arguments unused. |
warn_partial |
( |
Details
A covariance structure can be parsed from a model definition formula or call. Generally, covariance structures defined using non-standard evaluation take the following form:
type( (visit, )* visit | (group /)? subject )
For example, formulas may include terms such as
us(time | subject) cp(time | group / subject) sp_exp(coord1, coord2 | group / subject)
Note that only sp_exp
(spatial) covariance structures may provide multiple
coordinates, which identify the Euclidean distance between the time points.
Value
A cov_struct()
object.
Methods (by class)
-
as.cov_struct(formula)
: When provided a formula, any specialized functions are assumed to be covariance structure definitions and must follow the form:y ~ xs + type( (visit, )* visit | (group /)? subject )
Any component on the right hand side of a formula is considered when searching for a covariance definition.
See Also
Other covariance types:
cov_struct()
,
covariance_types
Examples
# provide a covariance structure as a right-sided formula
as.cov_struct(~ csh(visit | group / subject))
# when part of a full formula, suppress warnings using `warn_partial = FALSE`
as.cov_struct(y ~ x + csh(visit | group / subject), warn_partial = FALSE)