Add a Tier to Knowledge

Adds a new tier to the Knowledge object, either at the start, end, or before/after an existing tier.

Usage

add_tier(kn, tier, before = NULL, after = NULL)

Arguments

kn

A Knowledge object.

tier

Bare symbol / character (label) or numeric literal.

before, after

Optional anchor relative to an existing tier label, tier index, or variable. Once the Knowledge object already has >= 1 tier, you must supply exactly one of these.

Value

The updated Knowledge object.

See also

Other knowledge functions: +.Knowledge(), add_exogenous(), add_to_tier(), add_vars(), as_bnlearn_knowledge(), as_pcalg_constraints(), as_tetrad_knowledge(), convert_tiers_to_forbidden(), deparse_knowledge(), forbid_edge(), get_tiers(), knowledge(), knowledge_to_caugi(), remove_edge(), remove_tiers(), remove_vars(), reorder_tiers(), reposition_tier(), require_edge(), seq_tiers(), unfreeze()

Examples

data(tpc_example)

# create Knowledge object using verbs
kn1 <- knowledge() |>
  add_vars(names(tpc_example)) |>
  add_tier(child) |>
  add_tier(old, after = child) |>
  add_tier(youth, before = old) |>
  add_to_tier(child ~ starts_with("child")) |>
  add_to_tier(youth ~ starts_with("youth")) |>
  add_to_tier(old ~ starts_with("oldage")) |>
  require_edge(child_x1 ~ youth_x3) |>
  forbid_edge(child_x2 ~ youth_x4) |>
  add_exogenous(child_x1) # synonym: add_exo()

# set kn1 to frozen
# (meaning you cannot add variables to the Knowledge object anymore)
# this is to get a true on the identical check
kn1$frozen <- TRUE

# create identical Knowledge object using DSL
kn2 <- knowledge(
  tpc_example,
  tier(
    child ~ starts_with("child"),
    youth ~ starts_with("youth"),
    old ~ starts_with("oldage")
  ),
  child_x1 %-->% youth_x3,
  child_x2 %!-->% youth_x4,
  exo(child_x1) # synonym: exogenous()
)

print(identical(kn1, kn2))
#> [1] TRUE

# cannot require an edge against tier direction
try(
  kn1 |> require_edge(oldage_x6 ~ child_x1)
)
#> Error : Edge(s) violate tier ordering: oldage_x6 --> child_x1

# cannot forbid and require same edge
try(
  kn1 |> forbid_edge(child_x1 ~ youth_x3)
)
#> Error : Edge(s) appear as both forbidden and required: child_x1 --> youth_x3