unnest_tokens: Split a column into tokens using the tokenizers package

Description Usage Arguments Details Examples

View source: R/unnest_tokens.R

Description

Split a column into tokens using the tokenizers package, splitting the table into one-token-per-row. This function supports non-standard evaluation through the tidyeval framework.

Usage

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unnest_tokens(tbl, output, input, token = "words", format = c("text", "man",
  "latex", "html", "xml"), to_lower = TRUE, drop = TRUE, collapse = NULL,
  ...)

Arguments

tbl

A data frame

output

Output column to be created as string or symbol.

input

Input column that gets split as string or symbol.

The output/input arguments are passed by expression and support quasiquotation; you can unquote strings and symbols.

token

Unit for tokenizing, or a custom tokenizing function. Built-in options are "words" (default), "characters", "ngrams", "skip_ngrams", "sentences", "lines", "paragraphs", and "regex". If a function, should take a character vector and return a list of character vectors of the same length.

format

Either "text", "man", "latex", "html", or "xml". If not text, this uses the hunspell tokenizer, and can tokenize only by "word"

to_lower

Whether to turn column lowercase.

drop

Whether original input column should get dropped. Ignored if the original input and new output column have the same name.

collapse

Whether to combine text with newlines first in case tokens (such as sentences or paragraphs) span multiple lines. If NULL, collapses when token method is "ngrams", "skip_ngrams", "sentences", "lines", "paragraphs", or "regex".

...

Extra arguments passed on to the tokenizer, such as n and k for "ngrams" and "skip_ngrams" or pattern for "regex".

Details

If the unit for tokenizing is ngrams, skip_ngrams, sentences, lines, paragraphs, or regex, the entire input will be collapsed together before tokenizing.

If format is anything other than "text", this uses the hunspell_parse tokenizer instead of the tokenizers package. This does not yet have support for tokenizing by any unit other than words.

Examples

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library(dplyr)
library(janeaustenr)

d <- data_frame(txt = prideprejudice)
d

d %>%
  unnest_tokens(word, txt)

d %>%
  unnest_tokens(sentence, txt, token = "sentences")

d %>%
  unnest_tokens(ngram, txt, token = "ngrams", n = 2)

d %>%
  unnest_tokens(ngram, txt, token = "skip_ngrams", n = 4, k = 2)

d %>%
  unnest_tokens(chapter, txt, token = "regex", pattern = "Chapter [\\d]")

# custom function
d %>%
  unnest_tokens(word, txt, token = stringr::str_split, pattern = " ")

# tokenize HTML
h <- data_frame(row = 1:2,
                text = c("<h1>Text <b>is</b>", "<a href='example.com'>here</a>"))

h %>%
  unnest_tokens(word, text, format = "html")

tidytext documentation built on Nov. 18, 2017, 9:03 a.m.