Tidy variance structure for the nlme package.

Returns a tibble with the following columns:

group

type of varFunc, along with the right hand side of the formula in parentheses e.g. "varExp(age | Sex)".

term

terms included in the formula of the variance model, specifically the names of the coefficients. If the value is fixed, it will be appended with " ; fixed".

estimate

estimated coefficient

estimated

This column is only included if some parameters are fixed. TRUE if the parameter is estimated and FALSE if the parameter is fixed.

Usage

# S3 method for class 'varFunc'
tidy(x, ...)

# S3 method for class 'varComb'
tidy(x, ...)

Arguments

x

An object of class varFunc, such as those used as the weights argument from the nlme package

...

Ignored

Value

If the varFunc is uninitialized or has no parameters, the function will return an empty tibble. Otherwise, it will return a tibble with names described in the details section.

Examples

if (FALSE) { # \dontrun{
if (require("nlme")) {
ChickWeight_arbitrary_group <- datasets::ChickWeight
ChickWeight_arbitrary_group$group_arb_n <-
  1 + (
    as.integer(ChickWeight_arbitrary_group$Chick) >
    median(as.integer(ChickWeight_arbitrary_group$Chick))
  )
ChickWeight_arbitrary_group$group_arb <- c("low", "high")[ChickWeight_arbitrary_group$group_arb_n]

fit_with_fixed <-
  lme(
    weight ~ Diet * Time,
    random = ~Time | Chick,
    data =ChickWeight_arbitrary_group,
    weights=varIdent(fixed=c("low"=5), form=~1|group_arb)
  )
# Show all parameters
tidy(fit_with_fixed)
# Exclude fixed parameters
tidy(fit_with_fixed) %>%
  filter(across(any_of("estimated"), ~.x))
}
} # }