pattern2id: Match patterns against token types

In quanteda/quanteda: Quantitative Analysis of Textual Data

Match patterns against token types

Description

Developer function to match regex, fixed or glob patterns against token types. This allows C++ function to perform fast searches in tokens object. C++ functions use a list of type IDs to construct a hash table, against which sub-vectors of tokens object are matched. This function constructs an index of glob patterns for faster matching.

pattern2fixed converts regex and glob patterns to fixed patterns.

Usage

pattern2id(
  pattern,
  types,
  valuetype = c("glob", "fixed", "regex"),
  case_insensitive = TRUE,
  keep_nomatch = FALSE,
  use_index = TRUE
)

pattern2fixed(
  pattern,
  types,
  valuetype = c("glob", "fixed", "regex"),
  case_insensitive = TRUE,
  keep_nomatch = FALSE,
  use_index = TRUE
)

Arguments

pattern	a character vector, list of character vectors, dictionary, or collocations object. See pattern for details.
types	token types against which patterns are matched
valuetype	the type of pattern matching: "glob" for "glob"-style wildcard expressions; "regex" for regular expressions; or "fixed" for exact matching. See valuetype for details.
case_insensitive	logical; if TRUE, ignore case when matching a pattern or dictionary values
keep_nomatch	keep patterns that did not match
use_index	construct index of types for quick search

Value

a list of integer vectors containing indices of matched types

pattern2fixed returns a list of character vectors containing types

Examples

types <- c("A", "AA", "B", "BB", "BBB", "C", "CC")

pats_regex <- list(c("^a$", "^b"), c("c"), c("d"))
pattern2id(pats_regex, types, "regex", case_insensitive = TRUE)

pats_glob <- list(c("a*", "b*"), c("c"), c("d"))
pattern2id(pats_glob, types, "glob", case_insensitive = TRUE)

pattern <- list(c("^a$", "^b"), c("c"), c("d"))
types <- c("A", "AA", "B", "BB", "BBB", "C", "CC")
pattern2fixed(pattern, types, "regex", case_insensitive = TRUE)

quanteda/quanteda documentation built on April 15, 2024, 7:59 a.m.