stringdist

• Approximate matching and string distance calculations for R.
• All distance and matching operations are system- and encoding-independent.
• Built for speed, using openMP for parallel computing.

The package offers the following main functions:

• stringdist computes pairwise distances between two input character vectors (shorter one is recycled)
• stringdistmatrix computes the distance matrix for one or two vectors
• stringsim computes a string similarity between 0 and 1, based on stringdist
• amatch is a fuzzy matching equivalent of R's native match function
• ain is a fuzzy matching equivalent of R's native %in% operator
• seq_dist, seq_distmatrix, seq_amatch and seq_ain for distances between, and matching of integer sequences.

These functions are built upon C-code that re-implements some common (weighted) string distance functions. Distance functions include:

• Hamming distance;
• Levenshtein distance (weighted)
• Restricted Damerau-Levenshtein distance (weighted, a.k.a. Optimal String Alignment)
• Full Damerau-Levenshtein distance
• Longest Common Substring distance
• Q-gram distance
• cosine distance for q-gram count vectors (= 1-cosine similarity)
• Jaccard distance for q-gram count vectors (= 1-Jaccard similarity)
• Jaro, and Jaro-Winkler distance
• Soundex-based string distance

Also, there are some utility functions:

• qgrams() tabulates the qgrams in one or more character vectors.
• seq_qrams() tabulates the qgrams (somtimes called ngrams) in one or more integer vectors.
• phonetic() computes phonetic codes of strings (currently only soundex)
• printable_ascii() is a utility function that detects non-printable ascii or non-ascii characters.

C API

Some of stringdist's underlying C functions can be called directly from C code in other packages. The description of the API can be found by either typing ?stringdist_api in the R console or open the vignette directly as follows:

vignette("stringdist_C-Cpp_api", package="stringdist")

Examples of packages that link to stringdist can be found here and here.

Resources

• A paper on stringdist has been published in the R-journal
• Slides of a talk given at te useR!2014 conference.