Find the neighbours of a hierarchical model

Given a hierarchical model, finds its outer neighbours, its inner neighbours, or both.

Usage

find_neighbour_hierarchies(
  modelstr,
  nlists = NA,
  keepmaineffects = TRUE,
  maxorder = nlists - 1,
  type = c("all", "outer", "inner")
)

Arguments

modelstr

A model string written in hierarchical form.

nlists

The total number of lists. If NA, it is inferred from the largest list number appearing in modelstr.

keepmaineffects

If TRUE, main effects are not removed when constructing inner neighbours.

maxorder

The maximum interaction order permitted in outer neighbours.

type

Which neighbours to return. "all" returns both inner and outer neighbours, "outer" returns only models obtained by adding a term, and "inner" returns only models obtained by removing a generator.

Value

A character vector containing the requested neighbouring hierarchical models.

Details

An outer neighbour is obtained by adding an interaction term all of whose subsets are already in the model.

An inner neighbour is obtained by removing one of the generators defining the hierarchical model. Removing a generator removes only the defining interaction term itself, not the lower-order terms that it implies. For example, removing the generator 123 from [123,34] yields [12,13,23,34], not [34]. Main effects are not removed when keepmaineffects = TRUE.

References

Silverman, B. W., Chan, L. and Vincent, K. (2024). Bootstrapping Multiple Systems Estimates to Account for Model Selection. Statistics and Computing, 34, 44. doi:10.1007/s11222-023-10346-9 .

Examples

modelstr <- "[12,23]"

find_neighbour_hierarchies(modelstr)
#> [1] "[23,1]"     "[12,3]"     "[12,13,23]"
find_neighbour_hierarchies(modelstr, type = "outer")
#> [1] "[12,13,23]"
find_neighbour_hierarchies(modelstr, type = "inner")
#> [1] "[23,1]" "[12,3]"