R/TokenComparator.R

In comparator: Comparison Functions for Clustering and Record Linkage

#' @include Comparator.R
NULL

#' Virtual Token Comparator Class 
#' 
#' @description Represents a comparator for pairs of token sequences.
#' 
#' @slot .Data a function that calls the elementwise method for this class, 
#'   with arguments `x`, `y` and `...`.
#' @slot symmetric a logical of length 1. If TRUE, the comparator is symmetric 
#'   in its arguments---i.e. `comparator(x, y)` is identical to 
#'   `comparator(y, x)`.
#' @slot distance a logical of length 1. If `TRUE`, the comparator produces  
#'   distances and satisfies `comparator(x, x) = 0`. The comparator may not 
#'   satisfy all of the properties of a distance metric.
#' @slot similarity a logical of length 1. If `TRUE`, the comparator produces 
#'   similarity scores.
#' @slot tri_inequal a logical of length 1. If `TRUE`, the comparator satisfies 
#'   the triangle inequality. This is only possible (but not guaranteed) if 
#'   `distance = TRUE` and `symmetric = TRUE`.
#' @slot ordered a logical of length 1. If TRUE, the comparator treats token 
#'   sequences as ordered, otherwise they are treated as unordered.
#' 
#' @export
setClass("TokenComparator", 
         slots = c(
           ordered = "logical"
         ), 
         prototype = structure(
           .Data = function(x, y, ...) 0,
           ordered = TRUE
         ),
         contains = c("VIRTUAL", "Comparator"), 
         validity = function(object) {
           errs <- character()
           if (length(object@ordered) != 1)
             errs <- c(errs, "`ordered` must be a logical vector of length 1")
           ifelse(length(errs) == 0, TRUE, errs)
         })