Author: Emil Hvitfeldt
Date: 2025-03-18

# Cookbook - Using more complex recipes involving text

#### Emil Hvitfeldt

#### 2025-03-18

Working to get textual data converted into numerical can be done in many different ways. The steps included in `textrecipes` should hopefully give you the flexibility to perform most of your desired text preprocessing tasks. This vignette will showcase examples that combine multiple steps.

This vignette will not do any modeling with the processed text as its purpose it to showcase flexibility and modularity. Therefore the only packages needed will be `recipes` and `textrecipes`. Examples will be performed on the `tate_text` data-set which is packaged with `modeldata`.

    library(recipes)
    library(textrecipes)
    library(modeldata)
    data("tate_text")

## Counting select words

Sometimes it is enough to know the counts of a handful of specific words. This can be easily achieved using the arguments `custom_stopword_source` and `keep = TRUE` in `step_stopwords`.

    words <- c("or", "and", "on")

    okc_rec <- recipe(~., data = tate_text) %>%
      step_tokenize(medium) %>%
      step_stopwords(medium, custom_stopword_source = words, keep = TRUE) %>%
      step_tf(medium)

    okc_obj <- okc_rec %>%
      prep()

    bake(okc_obj, tate_text) %>%
      select(starts_with("tf_medium"))
    #> # A tibble: 4,284 × 3
    #>    tf_medium_and tf_medium_on tf_medium_or
    #>            <int>        <int>        <int>
    #>  1             1            0            1
    #>  2             0            1            0
    #>  3             0            1            0
    #>  4             0            1            0
    #>  5             0            1            0
    #>  6             0            1            0
    #>  7             0            1            0
    #>  8             0            1            0
    #>  9             1            1            0
    #> 10             0            1            0
    #> # ℹ 4,274 more rows

## Removing words in addition to the stop words list

You might know of certain words you don’t want included which isn’t a part of the stop word list of choice. This can easily be done by applying the `step_stopwords` step twice, once for the stop words and once for your special words.

    stopwords_list <- c(
      "was", "she's", "who", "had", "some", "same", "you", "most",
      "it's", "they", "for", "i'll", "which", "shan't", "we're",
      "such", "more", "with", "there's", "each"
    )

    words <- c("sad", "happy")

    okc_rec <- recipe(~., data = tate_text) %>%
      step_tokenize(medium) %>%
      step_stopwords(medium, custom_stopword_source = stopwords_list) %>%
      step_stopwords(medium, custom_stopword_source = words) %>%
      step_tfidf(medium)

    okc_obj <- okc_rec %>%
      prep()

    bake(okc_obj, tate_text) %>%
      select(starts_with("tfidf_medium"))
    #> # A tibble: 4,284 × 951
    #>    tfidf_medium_1 tfidf_medium_10 tfidf_medium_100 tfidf_medium_11
    #>             <dbl>           <dbl>            <dbl>           <dbl>
    #>  1              0               0                0               0
    #>  2              0               0                0               0
    #>  3              0               0                0               0
    #>  4              0               0                0               0
    #>  5              0               0                0               0
    #>  6              0               0                0               0
    #>  7              0               0                0               0
    #>  8              0               0                0               0
    #>  9              0               0                0               0
    #> 10              0               0                0               0
    #> # ℹ 4,274 more rows
    #> # ℹ 947 more variables: tfidf_medium_12 <dbl>, tfidf_medium_13 <dbl>,
    #> #   tfidf_medium_133 <dbl>, tfidf_medium_14 <dbl>, tfidf_medium_15 <dbl>,
    #> #   tfidf_medium_151 <dbl>, tfidf_medium_16 <dbl>, tfidf_medium_160 <dbl>,
    #> #   tfidf_medium_16mm <dbl>, tfidf_medium_18 <dbl>, tfidf_medium_19 <dbl>,
    #> #   tfidf_medium_2 <dbl>, tfidf_medium_20 <dbl>, tfidf_medium_2000 <dbl>,
    #> #   tfidf_medium_201 <dbl>, tfidf_medium_21 <dbl>, tfidf_medium_22 <dbl>, …

## Letter distributions

Another thing one might want to look at is the use of different letters in a certain text. For this we can use the built-in character tokenizer and keep only the characters using the `step_stopwords` step.

    okc_rec <- recipe(~., data = tate_text) %>%
      step_tokenize(medium, token = "characters") %>%
      step_stopwords(medium, custom_stopword_source = letters, keep = TRUE) %>%
      step_tf(medium)

    okc_obj <- okc_rec %>%
      prep()

    bake(okc_obj, tate_text) %>%
      select(starts_with("tf_medium"))
    #> # A tibble: 4,284 × 26
    #>    tf_medium_a tf_medium_b tf_medium_c tf_medium_d tf_medium_e tf_medium_f
    #>          <int>       <int>       <int>       <int>       <int>       <int>
    #>  1           1           0           2           3           4           0
    #>  2           1           0           1           0           2           0
    #>  3           1           0           1           0           2           0
    #>  4           1           0           1           0           2           0
    #>  5           3           0           1           0           0           0
    #>  6           3           0           1           0           0           0
    #>  7           3           0           2           0           1           0
    #>  8           1           0           1           1           1           0
    #>  9           5           0           1           1           0           0
    #> 10           1           0           0           0           1           0
    #> # ℹ 4,274 more rows
    #> # ℹ 20 more variables: tf_medium_g <int>, tf_medium_h <int>, tf_medium_i <int>,
    #> #   tf_medium_j <int>, tf_medium_k <int>, tf_medium_l <int>, tf_medium_m <int>,
    #> #   tf_medium_n <int>, tf_medium_o <int>, tf_medium_p <int>, tf_medium_q <int>,
    #> #   tf_medium_r <int>, tf_medium_s <int>, tf_medium_t <int>, tf_medium_u <int>,
    #> #   tf_medium_v <int>, tf_medium_w <int>, tf_medium_x <int>, tf_medium_y <int>,
    #> #   tf_medium_z <int>

## TF-IDF of ngrams of stemmed tokens

Sometimes fairly complicated computations are needed. Here we would like the term frequency inverse document frequency (TF-IDF) of the most common 500 ngrams done on stemmed tokens. It is quite a handful and would seldom be included as an option in most other libraries. But the modularity of `textrecipes` makes this task fairly easy.

First we will tokenize according to words, then stem those words. We will then paste together the stemmed tokens using `step_untokenize` so we are back at strings that we then tokenize again but this time using the ngram tokenizers. Lastly just filtering and tfidf as usual.

    okc_rec <- recipe(~., data = tate_text) %>%
      step_tokenize(medium, token = "words") %>%
      step_stem(medium) %>%
      step_untokenize(medium) %>%
      step_tokenize(medium, token = "ngrams") %>%
      step_tokenfilter(medium, max_tokens = 500) %>%
      step_tfidf(medium)

    okc_obj <- okc_rec %>%
      prep()

    bake(okc_obj, tate_text) %>%
      select(starts_with("tfidf_medium"))
    #> # A tibble: 4,284 × 499
    #>    `tfidf_medium_100 digit print` tfidf_medium_16 mm bl…¹ tfidf_medium_16 mm p…²
    #>                             <dbl>                   <dbl>                  <dbl>
    #>  1                              0                       0                      0
    #>  2                              0                       0                      0
    #>  3                              0                       0                      0
    #>  4                              0                       0                      0
    #>  5                              0                       0                      0
    #>  6                              0                       0                      0
    #>  7                              0                       0                      0
    #>  8                              0                       0                      0
    #>  9                              0                       0                      0
    #> 10                              0                       0                      0
    #> # ℹ 4,274 more rows
    #> # ℹ abbreviated names: ¹​`tfidf_medium_16 mm black`,
    #> #   ²​`tfidf_medium_16 mm project`
    #> # ℹ 496 more variables: `tfidf_medium_16 mm shown` <dbl>,
    #> #   `tfidf_medium_16mm shown a` <dbl>, `tfidf_medium_2 aluminium panel` <dbl>,
    #> #   `tfidf_medium_2 digit print` <dbl>, `tfidf_medium_2 lithograph on` <dbl>,
    #> #   `tfidf_medium_2 monitor colour` <dbl>, …