Partition a set of catalogue rows into always / maybe / unreachable

A question with no display logic is always shown. A question with display logic is unreachable only when its logic is shown to be false on this path: the questions it refers to that are not on the path (or are themselves unreachable) are unanswered and not displayed, so their conditions have fixed values, and if the logic is then false whatever the on-path answers are, the question can never be shown. Otherwise it is maybe. So a question whose logic is "Q9 is selected OR Q2 is selected" stays maybe when only Q9 is off the path, and "Q9 is not selected" is maybe (in fact always true) when Q9 is off the path.

Usage

classify_reachability(catalogue, path_qids, display_logic = NULL)

Arguments

catalogue: Catalogue rows (needs question_id, has_display_logic, display_logic_refs).
path_qids: Character vector of every question id on the path.
display_logic: Optional named list, by question id, of each question's Qualtrics DisplayLogic tree (a question payload's $DisplayLogic). Without it the logic cannot be evaluated, so no question is classed unreachable: every question with display logic is maybe. resolve_paths() supplies it from the survey.

Value

A list with character vectors always, maybe, unreachable.

Details

Unknown conditions are treated as independent, so the rule can leave a question as maybe that could be ruled out, but never marks a question unreachable wrongly (within the conditions it understands; embedded-data and other non-question conditions are always treated as unknown).

Examples

qsf_path <- system.file("extdata", "demo_travel_survey.qsf",
                         package = "surveyBurden")
catalogue <- parse_qsf(qsf_path)
reach <- classify_reachability(catalogue, catalogue$question_id)
lengths(reach)
#>      always       maybe unreachable 
#>          20           6           0