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tidytext: Text mining using tidy tools <img src="man/figures/tidytext.png" align="right" />

Authors: Julia Silge, David Robinson<br/> License: MIT

Using tidy data principles can make many text mining tasks easier, more effective, and consistent with tools already in wide use. Much of the infrastructure needed for text mining with tidy data frames already exists in packages like dplyr, broom, tidyr, and ggplot2. In this package, we provide functions and supporting data sets to allow conversion of text to and from tidy formats, and to switch seamlessly between tidy tools and existing text mining packages. Check out our book to learn more about text mining using tidy data principles.

Installation

You can install this package from CRAN:

install.packages("tidytext")

Or you can install the development version from GitHub with remotes:

library(remotes)
install_github("juliasilge/tidytext")

Tidy text mining example: the `unnest_tokens` function

The novels of Jane Austen can be so tidy! Let’s use the text of Jane Austen’s 6 completed, published novels from the janeaustenr package, and transform them to a tidy format. janeaustenr provides them as a one-row-per-line format:

library(janeaustenr)
library(dplyr)

original_books <- austen_books() %>%
  group_by(book) %>%
  mutate(line = row_number()) %>%
  ungroup()

original_books
#> # A tibble: 73,422 × 3
#>    text                    book                 line
#>    <chr>                   <fct>               <int>
#>  1 "SENSE AND SENSIBILITY" Sense & Sensibility     1
#>  2 ""                      Sense & Sensibility     2
#>  3 "by Jane Austen"        Sense & Sensibility     3
#>  4 ""                      Sense & Sensibility     4
#>  5 "(1811)"                Sense & Sensibility     5
#>  6 ""                      Sense & Sensibility     6
#>  7 ""                      Sense & Sensibility     7
#>  8 ""                      Sense & Sensibility     8
#>  9 ""                      Sense & Sensibility     9
#> 10 "CHAPTER 1"             Sense & Sensibility    10
#> # ℹ 73,412 more rows

To work with this as a tidy dataset, we need to restructure it as one-token-per-row format. The unnest_tokens() function is a way to convert a dataframe with a text column to be one-token-per-row:

library(tidytext)
tidy_books <- original_books %>%
  unnest_tokens(word, text)

tidy_books
#> # A tibble: 725,055 × 3
#>    book                 line word       
#>    <fct>               <int> <chr>      
#>  1 Sense & Sensibility     1 sense      
#>  2 Sense & Sensibility     1 and        
#>  3 Sense & Sensibility     1 sensibility
#>  4 Sense & Sensibility     3 by         
#>  5 Sense & Sensibility     3 jane       
#>  6 Sense & Sensibility     3 austen     
#>  7 Sense & Sensibility     5 1811       
#>  8 Sense & Sensibility    10 chapter    
#>  9 Sense & Sensibility    10 1          
#> 10 Sense & Sensibility    13 the        
#> # ℹ 725,045 more rows

This function uses the tokenizers package to separate each line into words. The default tokenizing is for words, but other options include characters, n-grams, sentences, lines, paragraphs, or separation around a regex pattern.

Now that the data is in a one-word-per-row format, we can manipulate it with tidy tools like dplyr. We can remove stop words (available via the function get_stopwords()) with an anti_join().

tidy_books <- tidy_books %>%
  anti_join(get_stopwords())

We can also use count() to find the most common words in all the books as a whole.

tidy_books %>%
  count(word, sort = TRUE) 
#> # A tibble: 14,375 × 2
#>    word      n
#>    <chr> <int>
#>  1 mr     3015
#>  2 mrs    2446
#>  3 must   2071
#>  4 said   2041
#>  5 much   1935
#>  6 miss   1855
#>  7 one    1831
#>  8 well   1523
#>  9 every  1456
#> 10 think  1440
#> # ℹ 14,365 more rows

Sentiment analysis can be implemented as an inner join. Three sentiment lexicons are available via the get_sentiments() function. Let’s examine how sentiment changes across each novel. Let’s find a sentiment score for each word using the Bing lexicon, then count the number of positive and negative words in defined sections of each novel.

library(tidyr)
get_sentiments("bing")
#> # A tibble: 6,786 × 2
#>    word        sentiment
#>    <chr>       <chr>    
#>  1 2-faces     negative 
#>  2 abnormal    negative 
#>  3 abolish     negative 
#>  4 abominable  negative 
#>  5 abominably  negative 
#>  6 abominate   negative 
#>  7 abomination negative 
#>  8 abort       negative 
#>  9 aborted     negative 
#> 10 aborts      negative 
#> # ℹ 6,776 more rows

janeaustensentiment <- tidy_books %>%
  inner_join(get_sentiments("bing"), by = "word", relationship = "many-to-many") %>% 
  count(book, index = line %/% 80, sentiment) %>% 
  pivot_wider(names_from = sentiment, values_from = n, values_fill = 0) %>% 
  mutate(sentiment = positive - negative)

janeaustensentiment
#> # A tibble: 920 × 5
#>    book                index negative positive sentiment
#>    <fct>               <dbl>    <int>    <int>     <int>
#>  1 Sense & Sensibility     0       16       32        16
#>  2 Sense & Sensibility     1       19       53        34
#>  3 Sense & Sensibility     2       12       31        19
#>  4 Sense & Sensibility     3       15       31        16
#>  5 Sense & Sensibility     4       16       34        18
#>  6 Sense & Sensibility     5       16       51        35
#>  7 Sense & Sensibility     6       24       40        16
#>  8 Sense & Sensibility     7       23       51        28
#>  9 Sense & Sensibility     8       30       40        10
#> 10 Sense & Sensibility     9       15       19         4
#> # ℹ 910 more rows

Now we can plot these sentiment scores across the plot trajectory of each novel.

library(ggplot2)

ggplot(janeaustensentiment, aes(index, sentiment, fill = book)) +
  geom_col(show.legend = FALSE) +
  facet_wrap(vars(book), ncol = 2, scales = "free_x")

For more examples of text mining using tidy data frames, see the tidytext vignette.

Tidying document term matrices

Some existing text mining datasets are in the form of a DocumentTermMatrix class (from the tm package). For example, consider the corpus of 2246 Associated Press articles from the topicmodels dataset.

library(tm)
data("AssociatedPress", package = "topicmodels")
AssociatedPress
#> <<DocumentTermMatrix (documents: 2246, terms: 10473)>>
#> Non-/sparse entries: 302031/23220327
#> Sparsity           : 99%
#> Maximal term length: 18
#> Weighting          : term frequency (tf)

If we want to analyze this with tidy tools, we need to transform it into a one-row-per-term data frame first with a tidy() function. (For more on the tidy verb, see the broom package).

tidy(AssociatedPress)
#> # A tibble: 302,031 × 3
#>    document term       count
#>       <int> <chr>      <dbl>
#>  1        1 adding         1
#>  2        1 adult          2
#>  3        1 ago            1
#>  4        1 alcohol        1
#>  5        1 allegedly      1
#>  6        1 allen          1
#>  7        1 apparently     2
#>  8        1 appeared       1
#>  9        1 arrested       1
#> 10        1 assault        1
#> # ℹ 302,021 more rows

We could find the most negative documents:

ap_sentiments <- tidy(AssociatedPress) %>%
  inner_join(get_sentiments("bing"), by = c(term = "word")) %>%
  count(document, sentiment, wt = count) %>%
  pivot_wider(names_from = sentiment, values_from = n, values_fill = 0) %>%
  mutate(sentiment = positive - negative) %>%
  arrange(sentiment)

Or we can join the Austen and AP datasets and compare the frequencies of each word:

comparison <- tidy(AssociatedPress) %>%
  count(word = term) %>%
  rename(AP = n) %>%
  inner_join(count(tidy_books, word)) %>%
  rename(Austen = n) %>%
  mutate(AP = AP / sum(AP),
         Austen = Austen / sum(Austen))


comparison
#> # A tibble: 4,730 × 3
#>    word             AP     Austen
#>    <chr>         <dbl>      <dbl>
#>  1 abandoned 0.000170  0.00000493
#>  2 abide     0.0000291 0.0000197 
#>  3 abilities 0.0000291 0.000143  
#>  4 ability   0.000238  0.0000148 
#>  5 able      0.000664  0.00151   
#>  6 abroad    0.000194  0.000178  
#>  7 abrupt    0.0000291 0.0000247 
#>  8 absence   0.0000776 0.000547  
#>  9 absent    0.0000436 0.000247  
#> 10 absolute  0.0000533 0.000128  
#> # ℹ 4,720 more rows

library(scales)
ggplot(comparison, aes(AP, Austen)) +
  geom_point(alpha = 0.5) +
  geom_text(aes(label = word), check_overlap = TRUE,
            vjust = 1, hjust = 1) +
  scale_x_log10(labels = percent_format()) +
  scale_y_log10(labels = percent_format()) +
  geom_abline(color = "red")

For more examples of working with objects from other text mining packages using tidy data principles, see the vignette on converting to and from document term matrices.

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