Pipe operator

Description

See magrittr::%>% for details.

Usage

lhs %>% rhs

Constructs a Verbal Expression

Description

Add this to the beginning of every verbal expression chain. This simply returns an empty character vector so that the next step in the chain can provide a value without explicitly writing value = "blah".

Usage

rx()

Examples

rx()
# this
rx() %>%
 rx_find("cat") %>%
 rx_anything() %>%
 rx_find("dog")
# instead of
rx_find(value = "cat") %>%
 rx_anything() %>%
 rx_find("dog")

Match alphanumeric characters.

Description

Matches both letters (case insensitive) and numbers (a through z and 0 through 9).

Usage

rx_alnum(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_alnum()
rx_alnum(inverse = TRUE)
# create an expression
x <- rx_alnum()
# create input
string <- "Apple 1!"
# extract match
regmatches(string, gregexpr(x, string))

Match alphabetic characters.

Description

Matches letters (case insensitive) only.

Usage

rx_alpha(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_alpha()
rx_alpha(inverse = TRUE)
# create an expression
x <- rx_alpha()
# create input
string <- "Apple 1!"
# extract match
regmatches(string, gregexpr(x, string))

Match any of these characters exactly once.

Description

Constructs a character class, sometimes called a character set. With this particular expression, you can tell the regex engine to match only one out of several characters. It does this by simply placing the characters you want to match between square brackets.

Usage

rx_any_of(.data = NULL, value)

Arguments

References

Character class: https://www.regular-expressions.info/charclass.html

Examples

rx_any_of(value = "abc")
# create an expression
x <- rx_any_of(value = "abc")
grepl(x, "c") # should be true
grepl(x, "d") # should be false
y <- rx() %>%
 rx_find("gr") %>%
 rx_any_of("ae") %>%
 rx_find("y")
regmatches("gray", regexec(y, "gray"))[[1]]
regmatches("grey", regexec(y, "grey"))[[1]]

Match any character(s) any (including zero) number of times.

Description

This expression will match everything except line breaks using the dot and the star. The Dot . is a metacharacter and the Star * is a quantifier. When combined the expression is considered greedy because it will match everything (except line breaks) 0 or more times.

Usage

rx_anything(.data = NULL, mode = "greedy")

Arguments

References

Dot: https://www.regular-expressions.info/dot.html

Star Quantifier: https://www.regular-expressions.info/repeat.html

Greedy and Lazy Quantifiers: https://www.regular-expressions.info/repeat.html#greedy

Examples

rx_anything()
rx_anything(mode = "lazy")
x <- rx() %>%
 rx_start_of_line() %>%
 rx_anything() %>%
 rx_end_of_line()
grepl(x, "anything!") # this should be true
grepl(rx_anything(), "") # this should be true
grepl(rx_something(), "") # this should be false

Match any character(s) except these any (including zero) number of times.

Description

This expression will match everything except whatever characters the user specifies in the value parameter. It does this by adding a caret symbol ^ at the beginning of a character set []. Typing a caret after the opening square bracket negates the character class. The result is that the character class matches any character that is not in the character class. Unlike the dot, negated character classes also match (invisible) line break characters. If you don't want a negated character class to match line breaks, you need to include the line break characters in the class.

Usage

rx_anything_but(.data = NULL, value, mode = "greedy")

Arguments

References

Character Class: https://www.regular-expressions.info/charclass.html

Examples

rx_anything_but(value = "abc")

Negative lookaround functions

Description

This function facilitates matching by providing negative assurances for surrounding symbols/groups of symbols. It allows for building expressions that are dependent on context of occurrence.

Usage

rx_avoid_prefix(.data = NULL, value)
rx_avoid_suffix(.data = NULL, value)

Arguments

Examples

# matches any number of digits, but not preceded by "USD"
rx() %>%
 rx_avoid_prefix('USD') %>%
 rx_digit() %>%
 rx_one_or_more()
#matches a digit, but not followed by " dollars"
rx() %>%
 rx_digit() %>%
 rx_avoid_suffix(' dollars')

Begin a capture group.

Description

Begin a capture group.

Usage

rx_begin_capture(.data = NULL)

Arguments

Details

Capture groups are used to extract data from within the regular expression match for further processing.

Match a digit (0–9).

Description

The function rx_digit()looks for tabs with the following expression: %%d and matches single digit. Plural version matches specified number of digits n (equivalent to rx_digit() %>% rx_count(n)).

Usage

rx_digit(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_digit()
rx_digit(inverse = TRUE)
# create an expression
x <- rx_digit()
# create input
string <- "1 apple"
# extract match
regmatches(string, regexpr(x, string))

Alternatively, match either expression.

Description

Expression to match instead. If both expressions exists, both will be returned. This just adds the vertical bar | often called an alternator which allows the user to find this or that, or both!

Usage

rx_either_of(.data, ...)

Arguments

Examples

x <- rx() %>%
 rx_either_of("cat", "dog") %>%
 rx_space() %>%
 rx_find("food")
string <- c("dog food", "cat food", "fish food")
grep(x, string, value = TRUE)

End a capture group.

Description

End a capture group.

Usage

rx_end_capture(.data = NULL)

Arguments

Details

Capture groups are used to extract data from within the regular expression match for further processing.

Match the expression only if it appears till the end of the line.

Description

Control whether to match the expression only if it appears till the end of the line. Basically, append a $ to the end of the expression. The dollar sign is considered an anchor and matches the position of characters. It can be used to "anchor" the regex match at a certain position, in this case the dollar sign matches right after the last character in the string.

Usage

rx_end_of_line(.data = NULL, enable = TRUE)

Arguments

References

Anchors: https://www.regular-expressions.info/anchors.html

Examples

rx_end_of_line(enable = TRUE)
rx_end_of_line(enable = FALSE)
rx_end_of_line("abc", enable = TRUE)
# create expression
x <- rx() %>%
 rx_start_of_line(FALSE) %>%
 rx_find("apple") %>%
 rx_end_of_line()
grepl(x, "apples") # should be false
grepl(x, "apple") # should be true

Match an expression.

Description

Identify a specific pattern exactly.

Usage

rx_find(.data = NULL, value)

Arguments

References

Capturing group: https://www.regular-expressions.info/brackets.html

Stack Overflow: https://stackoverflow.com/questions/3512471

Examples

rx_find(value = "apple")
# create expression
x <- rx_find(value = "apples")
grepl(x, "apple") # should be false
grepl(x, "apples") # should be true

Match a line break.

Description

This expression looks for line breaks, both Unix and Windows style by using the appropriate non printable characters.

Usage

rx_line_break(.data = NULL)

Arguments

References

Unix style: https://codepoints.net/U+000A

Windows style: https://codepoints.net/U+000D

Non printable character: https://www.regular-expressions.info/nonprint.html

Examples

rx_line_break()
# create an expression
x <- rx_line_break()
# create input
string <- "foo\nbar"
# extract match
regmatches(string, regexpr(x, string))

Match lower case letters.

Description

Matches lower case letters only.

Usage

rx_lowercase(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_lowercase()
rx_lowercase(inverse = TRUE)
# create an expression
x <- rx_lowercase()
y <- rx_lowercase(inverse = TRUE)
# create input
string <- "Apple 1!"
# extract match
regmatches(string, gregexpr(x, string))
regmatches(string, gregexpr(y, string))

Optionally match an expression.

Description

This expression uses a quantifier ? to optionally match things. Specifically, the question mark makes the preceding token in the regular expression optional.

Usage

rx_maybe(.data = NULL, value)

Arguments

References

Quantifiers: https://www.regular-expressions.info/optional.html

Examples

rx_maybe(value = "abc")
# create expression
x <- rx() %>%
 rx_start_of_line() %>%
 rx_maybe("abc") %>%
 rx_end_of_line(enable = FALSE)
grepl(x, "xyz") # should be true

Match the previous group any number of times.

Description

Match the previous group any number of times.

Usage

rx_multiple(.data = NULL, value = NULL, min = NULL, max = NULL)

Arguments

Match the previous stuff zero or many times.

Description

This function simply adds a * to the end of the expression.

Usage

rx_none_or_more(.data = NULL, mode = "greedy")

Arguments

Examples

rx_none_or_more()
# create an expression
x <- rx() %>%
 rx_find("a") %>%
 rx_none_or_more()
# create input
input <- "aaa"
# extract match
regmatches(input, regexpr(x, input))

Ensure that the parameter does not follow.

Description

This expression uses a negative lookahead to ensure the value given does not follow the previous verbal expression, perl = TRUE is required. For example, if you were to look for the letter q but not the letter u you might translate this to, "find the letter q everytime the letter u does not come after it".

Usage

rx_not(.data = NULL, value)

Arguments

References

Negative lookahead: https://www.regular-expressions.info/lookaround.html

Examples

rx_not(value = "FEB-28")
# construct expression
x <- rx() %>%
 rx_start_of_line() %>%
 rx_find('FEB-29') %>%
 rx_not("FEB-28")
# create a string
string <- c("FEB-29-2017", "FEB-28-2017")
# extract matches, perl = TRUE is required for negative lookahead
regmatches(string, regexpr(x, string, perl = TRUE))
# another example
rx() %>%
 rx_find("q") %>%
 rx_not("u") %>%
 grepl(x = c("qu", "qa", "qq", "q", "q u"), perl = TRUE)

Match the previous stuff one or more times.

Description

This function simply adds a + to the end of the expression.

Usage

rx_one_or_more(.data = NULL, mode = "greedy")

Arguments

Examples

rx_one_or_more()
# create an expression
x <- rx() %>%
 rx_find("a") %>%
 rx_one_or_more()
# create input
input <- "aaa"
# extract match
regmatches(input, regexpr(x, input))

Match punctuation characters.

Description

Matches punctuation characters only: ! \" # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~.

Usage

rx_punctuation(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_punctuation()
rx_punctuation(inverse = TRUE)
# create an expression
x <- rx_punctuation()
# create input
string <- 'Apple 1!'
# extract match
regmatches(string, gregexpr(x, string))
# dont extract punctuation
y <- rx_punctuation(inverse = TRUE)
regmatches(string, gregexpr(y, string))

Match any character within the range defined by the parameters.

Description

Value parameter will be interpreted as pairs. For example, range(c('a', 'z', '0', '9')) will be interpreted to mean any character within the ranges a–z (ascii x–y) or 0–9 (ascii x–y). The method expects an even number of parameters; unpaired parameters are ignored.

Usage

rx_range(.data = NULL, value)

Arguments

Examples

rx_range(value = c('1', '3'))
# create an expression
x <- rx_range(value = c('1', '3'))
grepl(x, "2") # should be true
grepl(x, "4") # should be false

Positive lookaround functions

Description

This function facilitates matching by providing assurances for surrounding symbols/groups of symbols. It allows for building expressions that are dependent on context of occurrence.

Usage

rx_seek_prefix(.data = NULL, value)
rx_seek_suffix(.data = NULL, value)

Arguments

Examples

# this will match anything between square brackets
rx() %>%
 rx_seek_prefix("[") %>%
 rx_anything("lazy") %>%
 rx_seek_suffix(']')

Match any character(s) at least once.

Description

This expression is almost identical to rx_anything() with one major exception, a + is used instead of a *. This means rx_something() expects something whereas anything() expects anything including... nothing!

Usage

rx_something(.data = NULL, mode = "greedy")

Arguments

References

Metacharacters: https://www.regular-expressions.info/characters.html#special

Greedy and Lazy Quantifiers: https://www.regular-expressions.info/repeat.html#greedy

Examples

rx_something()
# construct an expression
x <- rx_something()
grepl(x, "something!") # this should be true
grepl(x, "") # this should be false
grepl(rx_anything(), "") # this should be true

Match any character(s) except these at least once.

Description

This expression is almost identical to rx_anything_but() with one major exception, a + is used instead of a *. This means rx_something_but() expects something whereas rx_anything_but() expects anything including... nothing!

Usage

rx_something_but(.data = NULL, value, mode = "greedy")

Arguments

References

Metacharacters: https://www.regular-expressions.info/characters.html#special

Greedy and Lazy Quantifiers: https://www.regular-expressions.info/repeat.html#greedy

Examples

rx_something_but(value = "abc")
# create an expression
x <- rx_something_but(value = "python")
grepl(x, "R") # should be true
grepl(x, "py") # should be false

Match a space character.

Description

Matches a space character.

Usage

rx_space(.data = NULL, inverse = FALSE)

Arguments

Examples

# match space, default
rx_space()
# dont match space
rx_space(inverse = TRUE)
# create an expression
x <- rx_space()
# create input
string <- "1 apple\t"
# extract match
regmatches(string, regexpr(x, string))
# extract no whitespace by inverting behavior
y <- rx_space(inverse = TRUE)
regmatches(string, gregexpr(y, string))

Match the expression only if it appears from beginning of line.

Description

Control whether to match the expression only if it appears from the beginning of the line.

Usage

rx_start_of_line(.data = NULL, enable = TRUE)

Arguments

Examples

rx_start_of_line(enable = TRUE)
rx_start_of_line(enable = FALSE)
# create expression
x <- rx() %>%
 rx_start_of_line() %>%
 rx_find("apple")
grepl(x, "pineapple") # should be false
grepl(x, "apple") # should be true

Match a tab character.

Description

Match a tab character.

Usage

rx_tab(.data = NULL, inverse = FALSE)

Arguments

Details

This function is looks for tabs with the following expression: \t

1. Tab character: https://codepoints.net/U+0009

Examples

rx_tab()
rx_tab(inverse = TRUE)
# create an expression
x <- rx_tab()
# create input
string <- "foo\tbar"
# extract match
regmatches(string, regexpr(x, string))

Match upper case letters.

Description

Matches upper case letters only.

Usage

rx_uppercase(.data = NULL, inverse = FALSE)

Arguments

Examples

rx_uppercase()
rx_uppercase(inverse = TRUE)
# create an expression
x <- rx_uppercase()
y <- rx_uppercase(inverse = TRUE)
# create input
string <- "Apple 1!"
# extract match
regmatches(string, gregexpr(x, string))
regmatches(string, gregexpr(y, string))

Match a whitespace character.

Description

Match a whitespace character.

Usage

rx_whitespace(.data = NULL, inverse = FALSE)

Arguments

Details

Match a whitespace character (one of space, tab, carriage return, new line, vertical tab and form feed).

1. space: https://codepoints.net/U+0020

2. tab: https://codepoints.net/U+0009

3. carriage return: https://codepoints.net/U+000D

4. new line: https://codepoints.net/U+000

5. vertical tab: https://codepoints.net/U+000B

6. form feed: https://codepoints.net/U+000C

Examples

# match whitespace, default
rx_whitespace()
# dont match whitespace
rx_whitespace(inverse = TRUE)
# create an expression
x <- rx_whitespace()
# create input
string <- "1 apple"
# extract match
regmatches(string, regexpr(x, string))
# extract no whitespace by inverting behavior
y <- rx_whitespace(inverse = TRUE)
regmatches(string, gregexpr(y, string))

Control case-insensitive matching.

Description

Control case-insensitive matching.

Usage

rx_with_any_case(.data = NULL, enable = TRUE)

Arguments

Details

Equivalent to adding or removing the i modifier.

Examples

rx_with_any_case()
# case insensitive
x <- rx() %>%
 rx_find("abc") %>%
 rx_with_any_case()
# case sensitive
y <- rx() %>%
 rx_find("abc") %>%
 rx_with_any_case(enable = FALSE)
grepl(x, "ABC") # should be true
grepl(y, "ABC") # should be false

Match a word.

Description

Match a word—a string of word characters (a–z, A–Z, 0–9 or _). This function is looks for tabs with the following expression: \w+

Usage

rx_word(.data = NULL)

Arguments

Examples

rx_word()
# create an expression
x <- rx_word()
# create inputs
string1 <- "foo_bar"
string2 <- "foo-bar"
# extract matches
regmatches(string1, regexpr(x, string1))
regmatches(string2, regexpr(x, string2)) # doesn't match -

Match a word character.

Description

Match a word character (a–z, A–Z, 0–9 or _).

Usage

rx_word_char(.data = NULL)

Arguments

Examples

rx_word_char()
# Same as rx_word()
x <- rx_word_char() %>%
 rx_one_or_more()

Find beginning or end of a word.

Description

Match beginning or end of a word—a string consisting of of word characters (a–z, A–Z, 0–9 or _).

Usage

rx_word_edge(.data = NULL)

Arguments

Examples

rx_word_edge()
x <- rx() %>%
 rx_word_edge() %>%
 rx_alpha() %>%
 rx_one_or_more() %>%
 rx_word_edge()
# create inputs
string1 <- "foobar"
string2 <- "foo 23a bar"
# matches 'foobar'
regmatches(string1, regexpr(x, string1))
# matches 'foo' and 'bar' separately
regmatches(string2, gregexpr(x, string2))

Escape characters expected special by regex engines

Description

Takes a string and escapes all characters considered special by the regex engine. This is used internally when you add a string to the value parameter in most of the available functions. It is exported and usable externally for users that want to escape all special characters in their desired match. The following special characters are escaped . | * ? + ( ) { } ^ $ \ : = [ ]

Usage

sanitize(x)

Arguments

Examples

sanitize("^")
sanitize("^+")
sanitize("^+?")