unglue | R Documentation |
The functions unglue_data()
, unglue()
, unglue_vec()
and unglue_unnest()
extract matched substrings using a syntax inspired from glue::glue()
.
Simple cases don't require regex knowledge at all.
unglue(x, patterns, open = "{", close = "}", convert = FALSE, multiple = NULL)
unglue_data(
x,
patterns,
open = "{",
close = "}",
convert = FALSE,
multiple = NULL,
na = NA_character_
)
unglue_vec(
x,
patterns,
var = 1,
open = "{",
close = "}",
convert = FALSE,
multiple = NULL,
na = NA_character_
)
unglue_unnest(
data,
col,
patterns,
open = "{",
close = "}",
remove = TRUE,
convert = FALSE,
multiple = NULL,
na = NA_character_
)
x |
a character vector to unglue. |
patterns |
a character vector or a list of character vectors, if a list,
items will be pasted using an empty separator ( |
open |
The opening delimiter. |
close |
The closing delimiter. |
convert |
If |
multiple |
The aggregation function to use if several subpatterns are
named the same, by default no function is used and subpatterns named the
same will match the same value. If a function is provided it will be fed
the conflicting values as separate arguments. Formula notation
is supported if the package |
na |
string to use when there is no match |
var |
for |
data |
a data frame. |
col |
column containing the character vector to extract values from. |
remove |
whether to remove the column |
Depending on the task you might want:
unglue_data()
to return a data frame from a character vector,
just as glue::glue_data()
does in reverse
unglue()
to return a list of data frames containing the matches
unglue_vec()
to extract one value by element of x
, chosen by index or by
name.
unglue_unnest()
to extract value from a column of a data frame to new columns
To build the relevant regex pattern special characters will be escaped in the
input pattern and the subpatterns will be replaced with (.*?)
if in standard
"{foo}"
form. An alternate regular expression can be provided after =
so that
"{foo=\\d}"
will be translated into "(\\d)"
.
Sometimes we might want to use regex to match a part of the text that won't
be extracted, in these cases we just need to omit the name as in "{=\\d}"
.
unglue_unnest()
's name is a tribute to tidyr::unnest()
because
unglue_unnest(data, col, patterns)
returns a similar output as
dplyr::mutate(data, unglued = unglue(col, patterns)) %>% tidyr::unnest()
(without requiring any extra package).
It is also very close to tidyr::extract()
and efforts were made to make
the syntax consistent with the latter.
For unglue()
a list of one row data frames, for unglue_data
a
data frame, for unglue_unnest
the data frame input with additional columns
built from extracted values, for unglue_vec
an atomic vector.
# using an awample from ?glue::glue
if(require(magrittr) && require(glue)) {
glued_data <- mtcars %>% glue_data("{rownames(.)} has {hp} hp")
unglue_data(glued_data, "{rownames(.)} has {hp} hp")
}
facts <- c("Antarctica is the largest desert in the world!",
"The largest country in Europe is Russia!",
"The smallest country in Europe is Vatican!",
"Disneyland is the most visited place in Europe! Disneyland is in Paris!",
"The largest island in the world is Green Land!")
facts_df <- data.frame(id = 1:5, facts)
patterns <- c("The {adjective} {place_type} in {bigger_place} is {place}!",
"{place} is the {adjective} {place_type=[^ ]+} in {bigger_place}!{=.*}")
unglue_data(facts, patterns)
sentences <- c("666 is [a number]", "foo is [a word]",
"42 is [the answer]", "Area 51 is [unmatched]")
patterns <- c("{number=\\d+} is [{what}]", "{word=\\D+} is [{what}]")
unglue_data(sentences, patterns)
unglue_unnest(facts_df, facts, patterns)
unglue_unnest(facts_df, facts, patterns, remove = FALSE)
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