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View strings and matches

Source: R/view.R
str_view.Rd

str_view() is used to print the underlying representation of a string and to see how a pattern matches.

Matches are surrounded by <> and unusual whitespace (i.e. all whitespace apart from " " and "\n") are surrounded by {} and escaped. Where possible, matches and unusual whitespace are coloured blue and NAs red.

Usage

str_view(
  string,
  pattern = NULL,
  match = TRUE,
  html = FALSE,
  use_escapes = FALSE
)

Arguments

string

Input vector. Either a character vector, or something coercible to one.

pattern

Pattern to look for.

The default interpretation is a regular expression, as described in vignette("regular-expressions"). Use regex() for finer control of the matching behaviour.

Match a fixed string (i.e. by comparing only bytes), using fixed(). This is fast, but approximate. Generally, for matching human text, you'll want coll() which respects character matching rules for the specified locale.

Match character, word, line and sentence boundaries with boundary(). An empty pattern, "", is equivalent to boundary("character").

match

If pattern is supplied, which elements should be shown?

  • TRUE, the default, shows only elements that match the pattern.

  • NA shows all elements.

  • FALSE shows only elements that don't match the pattern.

If pattern is not supplied, all elements are always shown.

html

Use HTML output? If TRUE will create an HTML widget; if FALSE will style using ANSI escapes.

use_escapes

If TRUE, all non-ASCII characters will be rendered with unicode escapes. This is useful to see exactly what underlying values are stored in the string.

Examples

# Show special characters
str_view(c("\"\\", "\\\\\\", "fgh", NA, "NA"))
#> [1] │ "\
#> [2] │ \\\
#> [3] │ fgh
#> [4] │ NA
#> [5] │ NA

# A non-breaking space looks like a regular space:
nbsp <- "Hi\u00A0you"
nbsp
#> [1] "Hi you"
# But it doesn't behave like one:
str_detect(nbsp, " ")
#> [1] FALSE
# So str_view() brings it to your attention with a blue background
str_view(nbsp)
#> [1] │ Hi{\u00a0}you

# You can also use escapes to see all non-ASCII characters
str_view(nbsp, use_escapes = TRUE)
#> [1] │ Hi\u00a0you

# Supply a pattern to see where it matches
str_view(c("abc", "def", "fghi"), "[aeiou]")
#> [1] │ <a>bc
#> [2] │ d<e>f
#> [3] │ fgh<i>
str_view(c("abc", "def", "fghi"), "^")
#> [1] │ <>abc
#> [2] │ <>def
#> [3] │ <>fghi
str_view(c("abc", "def", "fghi"), "..")
#> [1] │ <ab>c
#> [2] │ <de>f
#> [3] │ <fg><hi>

# By default, only matching strings will be shown
str_view(c("abc", "def", "fghi"), "e")
#> [2] │ d<e>f
# but you can show all:
str_view(c("abc", "def", "fghi"), "e", match = NA)
#> [1] │ abc
#> [2] │ d<e>f
#> [3] │ fghi
# or just those that don't match:
str_view(c("abc", "def", "fghi"), "e", match = FALSE)
#> [1] │ abc
#> [3] │ fghi