Gravity Falls and Tidy Data Principles (Part 1)

Motivation

After reading The Life Changing Magic of Tidying Text and A tidy text analysis of Rick and Morty I wanted to do something similar for Rick and Morty and I did. Now I’m doing something similar for Gravity Falls.

In this post I’ll focus on the Tidy Data principles. However, here is the Github repo with the scripts to scrap the subtitles of Rick and Morty and other shows.

Note: If some images appear too small on your screen you can open them in a new tab to show them in their original size.

Let’s scrap

The subtools package returns a data frame after reading srt files. In addition to that resulting data frame I wanted to explicitly point the season and chapter of each line of the subtitles. To do that I had to scrap the subtitles and then use str_replace_all. To follow the steps clone the repo from Github:

git clone https://github.com/pachamaltese/rick_and_morty_tidy_text

Gravity Falls Can Be So Tidy

After reading the tidy file I created after scraping the subtitles, I use unnest_tokens to divide the subtitles in words. This function uses the tokenizers package to separate each line into words. The default tokenizing is for words, but other options include characters, sentences, lines, paragraphs, or separation around a regex pattern.

if (!require("pacman")) install.packages("pacman")
p_load(data.table, tidyr, tidytext, dplyr, ggplot2, viridis, ggstance, igraph, ggraph)
p_load_gh("dgrtwo/widyr")

gravity_falls_subs <- as_tibble(fread("../../data/2017-10-13-rick-and-morty-tidy-data/gravity_falls_subs.csv")) %>% 
  mutate(text = iconv(text, from = "", to = "ASCII")) %>% 
  drop_na()

gravity_falls_subs_tidy <- gravity_falls_subs %>% 
  unnest_tokens(word,text) %>% 
  anti_join(stop_words)

The data is in one-word-per-row format, and we can manipulate it with tidy tools like dplyr. For example, in the last chunk I used an anti_join to remove words such a “a”, “an” or “the”.

Then we can use count to find the most common words in all of Gravity Falls episodes as a whole.

gravity_falls_subs_tidy %>%
  count(word, sort = TRUE)
# A tibble: 7,541 x 2
   word       n
   <chr>  <int>
 1 mabel    456
 2 hey      453
 3 ha       416
 4 stan     369
 5 dipper   347
 6 gonna    341
 7 time     313
 8 yeah     291
 9 uh       264
10 guys     244
# ... with 7,531 more rows

Sentiment analysis can be done as an inner join. Three sentiment lexicons are in the tidytext package in the sentiment dataset. Let’s examine how sentiment changes changes during each season. 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 season.

bing <- sentiments %>%
  filter(lexicon == "bing") %>%
  select(-score)

bing
# A tibble: 6,788 x 3
   word        sentiment lexicon
   <chr>       <chr>     <chr>  
 1 2-faced     negative  bing   
 2 2-faces     negative  bing   
 3 a+          positive  bing   
 4 abnormal    negative  bing   
 5 abolish     negative  bing   
 6 abominable  negative  bing   
 7 abominably  negative  bing   
 8 abominate   negative  bing   
 9 abomination negative  bing   
10 abort       negative  bing   
# ... with 6,778 more rows
gravity_falls_sentiment <- gravity_falls_subs_tidy %>%
  inner_join(bing) %>% 
  count(episode_name, index = linenumber %/% 50, sentiment) %>% 
  spread(sentiment, n, fill = 0) %>% 
  mutate(sentiment = positive - negative) %>%
  left_join(gravity_falls_subs_tidy[,c("episode_name","season","episode")] %>% distinct()) %>% 
  arrange(season,episode) %>% 
  mutate(episode_name = paste(season,episode,"-",episode_name),
         season = factor(season, labels = paste("Season", 1:2))) %>% 
  select(episode_name, season, everything(), -episode)

gravity_falls_sentiment
# A tibble: 381 x 6
   episode_name                  season  index negative positive sentiment
   <chr>                         <fct>   <dbl>    <dbl>    <dbl>     <dbl>
 1 S01 E01 - Tourist Trapped     Season…     0       10        9        -1
 2 S01 E01 - Tourist Trapped     Season…     1       12        3        -9
 3 S01 E01 - Tourist Trapped     Season…     2       10        9        -1
 4 S01 E01 - Tourist Trapped     Season…     3       14        6        -8
 5 S01 E01 - Tourist Trapped     Season…     4       10        5        -5
 6 S01 E01 - Tourist Trapped     Season…     5       13        3       -10
 7 S01 E01 - Tourist Trapped     Season…     6        7        5        -2
 8 S01 E01 - Tourist Trapped     Season…     7        9        7        -2
 9 S01 E01 - Tourist Trapped     Season…     8        1        1         0
10 S01 E02 - The Legend of the … Season…     0        2       15        13
# ... with 371 more rows

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

ggplot(gravity_falls_sentiment, aes(index, sentiment, fill = season)) +
  geom_bar(stat = "identity", show.legend = FALSE) +
  facet_wrap(~season, nrow = 3, scales = "free_x", dir = "v") +
  theme_minimal(base_size = 13) +
  labs(title = "Sentiment in Gravity Falls",
       y = "Sentiment") +
  scale_fill_viridis(end = 0.75, discrete = TRUE) +
  scale_x_discrete(expand = c(0.02,0)) +
  theme(strip.text = element_text(hjust = 0)) +
  theme(strip.text = element_text(face = "italic")) +
  theme(axis.title.x = element_blank()) +
  theme(axis.ticks.x = element_blank()) +
  theme(axis.text.x = element_blank())

Looking at Units Beyond Words

Lots of useful work can be done by tokenizing at the word level, but sometimes it is useful or necessary to look at different units of text. For example, some sentiment analysis algorithms look beyond only unigrams (i.e. single words) to try to understand the sentiment of a sentence as a whole. These algorithms try to understand that I am not having a good day is a negative sentence, not a positive one, because of negation.

gravity_falls_sentences <- gravity_falls_subs %>% 
  group_by(season) %>% 
  unnest_tokens(sentence, text, token = "sentences") %>% 
  ungroup()

Let’s look at just one.

gravity_falls_sentences$sentence[200]
[1] "bwahhhh!"

We can use tidy text analysis to ask questions such as what are the most negative episodes in each of Gravity Falls’s seasons? First, let’s get the list of negative words from the Bing lexicon. Second, let’s make a dataframe of how many words are in each chapter so we can normalize for the length of chapters. Then, let’s find the number of negative words in each chapter and divide by the total words in each chapter. Which chapter has the highest proportion of negative words?

bingnegative <- sentiments %>%
  filter(lexicon == "bing", sentiment == "negative")

wordcounts <- gravity_falls_subs_tidy %>%
  group_by(season, episode) %>%
  summarize(words = n())

gravity_falls_subs_tidy %>%
  semi_join(bingnegative) %>%
  group_by(season, episode) %>%
  summarize(negativewords = n()) %>%
  left_join(wordcounts, by = c("season", "episode")) %>%
  mutate(ratio = negativewords/words) %>%
  top_n(1)
# A tibble: 2 x 5
# Groups:   season [2]
  season episode negativewords words ratio
  <chr>  <chr>           <int> <int> <dbl>
1 S01    E14               124   944 0.131
2 S02    E06               129   962 0.134

Networks of Words

Another function in widyr is pairwise_count, which counts pairs of items that occur together within a group. Let’s count the words that occur together in the lines of the first season.

gravity_falls_words <- gravity_falls_subs_tidy %>%
  filter(season == "S01")

word_cooccurences <- gravity_falls_words %>%
  pairwise_count(word, linenumber, sort = TRUE)

word_cooccurences
# A tibble: 471,288 x 3
   item1   item2       n
   <chr>   <chr>   <dbl>
 1 grunkle stan       90
 2 stan    grunkle    90
 3 stan    hey        70
 4 hey     stan       70
 5 hey     mabel      67
 6 mabel   hey        67
 7 hey     dipper     59
 8 dipper  hey        59
 9 mabel   dipper     57
10 dipper  mabel      57
# ... with 471,278 more rows

This can be useful, for example, to plot a network of co-occuring words with the igraph and ggraph packages.

set.seed(1717)

word_cooccurences %>%
  filter(n >= 25) %>%
  graph_from_data_frame() %>%
  ggraph(layout = "fr") +
  geom_edge_link(aes(edge_alpha = n, edge_width = n), edge_colour = "#a8a8a8") +
  geom_node_point(color = "darkslategray4", size = 8) +
  geom_node_text(aes(label = name), vjust = 2.2) +
  ggtitle(expression(paste("Word Network in Gravity Falls's ", 
                           italic("Season One")))) +
  theme_void()