Lookup: Lookup String Comparator

In comparator: Comparison Functions for Clustering and Record Linkage

Lookup String Comparator

Description

Compares a pair of strings x and y by retrieving their distance/similarity score from a provided lookup table.

Usage

Lookup(
  lookup_table,
  values_colnames,
  score_colname,
  default_match = 0,
  default_nonmatch = NA_real_,
  symmetric = TRUE,
  ignore_case = FALSE
)

Arguments

lookup_table	data frame containing distances/similarities for pairs of values
values_colnames	character vector containing the colnames corresponding to pairs of values (e.g. strings) in lookup_table
score_colname	name of column that contains distances/similarities in lookup_table
default_match	distance/similarity to use if the pair of values match exactly and do not appear in lookup_table. Defaults to 0.0.
default_nonmatch	distance/similarity to use if the pair of values are not an exact match and do not appear in lookup table. Defaults to NA.
symmetric	whether the underlying distance/similarity scores are symmetric. If TRUE lookup_table need only contain entries for one of the two pairs—i.e. an entry for value pair (y, x) is not required if an entry for (x, y) is already present.
ignore_case	a logical. If TRUE, case is ignored when comparing the strings.

Details

The lookup table should contain three columns corresponding to x, and y (values_colnames below) and the distance/similarity (score_colname below). If a pair of values x and y is not in the lookup table, a default distance/similarity is returned depending on whether x = y (default_match below) or x != y (default_nonmatch below).

Value

A Lookup instance is returned, which is an S4 class inheriting from StringComparator.

Examples

## Measure the distance between cities
lookup_table <- data.frame(x = c("Melbourne", "Melbourne", "Sydney"), 
                           y = c("Sydney", "Brisbane", "Brisbane"), 
                           dist = c(713.4, 1374.8, 732.5))

comparator <- Lookup(lookup_table, c("x", "y"), "dist")
comparator("Sydney", "Melbourne")
comparator("Melbourne", "Perth")

comparator documentation built on March 18, 2022, 6:15 p.m.