fuzzystring provides fast, flexible fuzzy string joins for data.frame and data.table objects using approximate string matching. It combines stringdist-based matching with a data.table backend and compiled C++ result assembly to reduce overhead in large joins while preserving standard join semantics.

Why fuzzystring?

Real-world identifiers rarely line up exactly. fuzzystring is designed for workloads such as:

• matching customer or company names with typos
• reconciling product catalogs with inconsistent labels
• linking survey responses to a controlled vocabulary
• joining reference tables to messy user input

The package includes:

• fuzzy inner, left, right, full, semi, and anti joins
• multiple stringdist methods, including OSA, Levenshtein, Damerau-Levenshtein, Jaro-Winkler, q-gram, cosine, jaccard, and soundex
• output that preserves the class of x (data.table, tibble, or base data.frame)
• optional distance columns for matched pairs
• case-insensitive matching
• adaptive candidate planning for single-column joins
• compiled C++ row expansion and result assembly across join modes

Installation

# Install from CRAN
install.packages("fuzzystring")
# Development version from GitHub
# pak::pak("PaulESantos/fuzzystring")
# remotes::install_github("PaulESantos/fuzzystring")

Quick start

library(fuzzystring)
x <- data.frame(
  name = c("Idea", "Premiom", "Very Good"),
  id = 1:3
)
y <- data.frame(
  approx_name = c("Ideal", "Premium", "VeryGood"),
  grp = c("A", "B", "C")
)
fuzzystring_inner_join(
  x, y,
  by = c(name = "approx_name"),
  max_dist = 2,
  distance_col = "distance"
)

Join families

fuzzystring_inner_join(x, y, by = c(name = "approx_name"), max_dist = 2)
fuzzystring_left_join(x, y, by = c(name = "approx_name"), max_dist = 2)
fuzzystring_right_join(x, y, by = c(name = "approx_name"), max_dist = 2)
fuzzystring_full_join(x, y, by = c(name = "approx_name"), max_dist = 2)
fuzzystring_semi_join(x, y, by = c(name = "approx_name"), max_dist = 2)
fuzzystring_anti_join(x, y, by = c(name = "approx_name"), max_dist = 2)

Distance methods

fuzzystring_inner_join(x, y, by = c(name = "approx_name"), method = "osa")
fuzzystring_inner_join(x, y, by = c(name = "approx_name"), method = "dl")
fuzzystring_inner_join(x, y, by = c(name = "approx_name"), method = "jw")
fuzzystring_inner_join(x, y, by = c(name = "approx_name"), method = "soundex")

Case-insensitive matching

fuzzystring_inner_join(
  x, y,
  by = c(name = "approx_name"),
  ignore_case = TRUE,
  max_dist = 1
)

Included example data

The package ships with misspellings, a dataset of common misspellings adapted from Wikipedia for examples and testing.

data(misspellings)
head(misspellings)

Performance

fuzzystring keeps more of the join execution on a compiled path than the original fuzzyjoin implementation. In practice, the package combines:

• data.table grouping and candidate planning
• adaptive blocking for single-column string joins
• compiled row expansion, row binding, and final assembly
• type-preserving handling of dates, datetimes, factors, and list-columns

The benchmark article summarizes a precomputed comparison against fuzzyjoin::stringdist_join() using the same methods and sample sizes:

• Getting started: https://paulesantos.github.io/fuzzystring/articles/getting_started.html
• Benchmark article: https://paulesantos.github.io/fuzzystring/articles/benchmark_fuzzyjoin_comparison.html

Multiple-column joins

fuzzystring_join() can match across more than one string column by applying the same distance method and threshold to each mapped column.

x_multi <- data.frame(
  first = c("Jon", "Maira"),
  last = c("Smyth", "Gonzales")
)
y_multi <- data.frame(
  first_ref = c("John", "Maria"),
  last_ref = c("Smith", "Gonzalez"),
  id = 1:2
)
fuzzystring_inner_join(
  x_multi, y_multi,
  by = c(first = "first_ref", last = "last_ref"),
  method = "osa",
  max_dist = 1
)

Related packages

• fuzzyjoin: original fuzzy join API that inspired this package
• stringdist: distance metrics
• data.table: high-performance tabular backend

Credits

fuzzystring builds on ideas popularized by fuzzyjoin, while reinterpreting the join pipeline around data.table and compiled C++ result assembly.