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Extract decision rules from a CHAID tree

Source: R/11_inspect.R
chaid_rules.Rd

Returns the condition that a case must satisfy to reach each terminal node (or each of the requested nodes) as a rule string.

Usage

chaid_rules(fit, nodes = NULL, format = c("text", "sql", "r"))

Arguments

fit

A fitted "chaid" object returned by chaid().

nodes

Integer vector of node ids. Defaults to all terminal nodes.

format

"text" (default) for human-readable conditions, "sql" for SQL WHERE clauses, or "r" for R logical expressions that reproduce the node assignment exactly when evaluated against the data.

Value

A data frame with columns node (integer id) and rule (character).

See also

chaid(), chaid_table()

Examples

fit <- chaid(Species ~ ., data = iris,
             control = chaid_control(min_parent = 30, min_child = 10))
chaid_rules(fit)
#>   node                       rule
#> 1    2        Petal.Length <= 1.6
#> 2    3 Petal.Length in (1.6, 3.8]
#> 3    4 Petal.Length in (3.8, 4.6]
#> 4    5 Petal.Length in (4.6, 4.9]
#> 5    6 Petal.Length in (4.9, 5.3]
#> 6    7         Petal.Length > 5.3
chaid_rules(fit, format = "sql")
#>   node
#> 1    2
#> 2    3
#> 3    4
#> 4    5
#> 5    6
#> 6    7
#>                                                                         rule
#> 1                                         Petal.Length <= 1.6000000000000001
#> 2 (Petal.Length > 1.6000000000000001 AND Petal.Length <= 3.7999999999999998)
#> 3 (Petal.Length > 3.7999999999999998 AND Petal.Length <= 4.5999999999999996)
#> 4 (Petal.Length > 4.5999999999999996 AND Petal.Length <= 4.9000000000000004)
#> 5 (Petal.Length > 4.9000000000000004 AND Petal.Length <= 5.2999999999999998)
#> 6                                          Petal.Length > 5.2999999999999998