consistency {QCAtools}

Compute the consistency value

Description

Computes the consistency score of "formula1 -> formula2" (sufficient condition) or "formula1 <- formula2" (necessary condition), depending on whether type is "->" or "<-". If type is "<->" it computes an equivalence score of formula1 and formula2 via the formula sum(min(X,Y))/(sum(max(X,Y))

Usage

consistency(formula1, type = "->", formula2, data)

Arguments

formula1

A string, list of strings or function representing a Boolean formula in disjunctive normal form

type

either "->", "<-" or "<->", depending on the direction of the implication that is to be evaluated

formula2

A string, list of strings or function representing a Boolean formula in disjunctive normal form

data

A data frame where the rows represent cases and the columns the sets. Column names must be as in the formula.

Details

Compute a consistency score for an implication/necessity/sufficiency statement.

If formula is a function, it must take a data.frame and return a vector.

If formula is a string or list of strings, the following conventions hold: Set names must be capitalized in the formula and the data; if they are lowercase, they are interpreted as the negation of the set. If formula is a string, logical 'or' is expressed as a '+', and logical 'and' as a '*'. If formula is a list of strings, the strings are assumed to be the dosjuncts and are concatenated with '+'. The formula must be in disjunctive normal form, i.e. it must be a disjunction of conjunctions of elementary or negated elementary sets. Example: A*b*C + a*B

Value

the consistency score of the implication described by formula1, type and formula2

Examples

require(QCA)
data(d.urban)
consistency("MLC + FRB", "->", "CP", d.urban)