Gegevens voorbereiden

Tijdens de Amerikaanse verkiezingen van 2016 werden Russische tweetbots gebruikt om voortdurend politieke retoriek te verspreiden onder zowel democraten als republikeinen. Je hebt een gegevensset met zulke tweets gekregen, russian_tweets. Je gaat deze tweets classificeren als links (democraat) of rechts (republikein). Voordat je een classificatiemodel kunt bouwen, moet je de tekst opschonen en voorbereiden voor modellering.

Deze oefening maakt deel uit van de cursus

Introductie tot Natural Language Processing in R

Cursus bekijken

Oefeninstructies

Rond het tokeniseren af door de tokens te stemmen.
Gebruik cast_dtm() om een document-termmatrix te maken.
Weeg de document-termmatrix met tf-idf-weging.
Print de matrix.

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Stem the tokens
russian_tokens <- russian_tweets %>%
  unnest_tokens(output = "word", token = "words", input = content) %>%
  anti_join(stop_words) %>%
  ___(word = ___(word))

# Create a document term matrix using TFIDF weighting
tweet_matrix <- russian_tokens %>%
  count(tweet_id, word) %>%
  ___(document = ___, term = ___,
           value = n, weighting = tm::___)

# Print the matrix details 
___

Code bewerken en uitvoeren

Deze oefening maakt deel uit van de cursus

Introductie tot Natural Language Processing in R

SkillTag.level.intermediateSkillTag.label

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Begin de cursus gratis

Chapter 1 of Introduction to Natural Langauge Processing prepares you for running your first analysis on text. You will explore regular expressions and tokenization, two of the most common components of most analysis tasks. With regular expressions, you can search for any pattern you can think of, and with tokenization, you can prepare and clean text for more sophisticated analysis. This chapter is necessary for tackling the techniques we will learn in the remaining chapters of this course.

Exercise 1: Regular expression basics Exercise 2: Practicing syntax with grep Exercise 3: Exploring regular expression functions.Exercise 4: Tokenization Exercise 5: tidytext functions Exercise 6: Tokenization: sentences Exercise 7: Text cleaning basics Exercise 8: Text preprocessing: remove stop words Exercise 9: Text preprocessing: Stemming

In this chapter, you will learn the most common and studied ways to analyze text. You will look at creating a text corpus, expanding a bag-of-words representation into a TFIDF matrix, and use cosine-similarity metrics to determine how similar two pieces of text are to each other. You build on your foundations for practicing NLP before you dive into applications of NLP in chapters 3 and 4.

Exercise 1: Understanding an R corpus Exercise 2: Explore an R corpus Exercise 3: Creating a tibble from a corpus Exercise 4: Creating a corpus Exercise 5: The bag-of-words representation Exercise 6: Practice BoW Exercise 7: BoW Example Exercise 8: Sparse matrices Exercise 9: The TFIDF Exercise 10: Manual calculations Exercise 11: TFIDF Practice Exercise 12: Cosine Similarity Exercise 13: An example of failing at text analysis Exercise 14: Cosine similarity example

Chapter 3 focuses on two common text analysis approaches, classification modeling, and topic modeling. If you are working on text analysis projects, you will inevitably use one or both of these methods. This chapter teaches you how to perform both techniques and provides insight into how to approach these techniques from a practical point of you.

Exercise 1: Tekst voorbereiden voor modelleren Exercise 2: Gegevens voorbereiden

Huidige oefening

Exercise 3: Schaarse termen verwijderen Exercise 4: Classificatiemodellering Exercise 5: Voorbeeld van classificatiemodel Exercise 6: Confusion matrices Exercise 7: TFIDF-tibble vs dtm Exercise 8: Introductie tot topic modeling Exercise 9: Oefenen met LDA Exercise 10: Onderwerpen toekennen aan documenten Exercise 11: LDA in de praktijk Exercise 12: Perplexity testen Exercise 13: LDA-resultaten beoordelen

In chapter 4 we cover two staples of natural language processing, sentiment analysis, and word embeddings. These are two analysis techniques that are a must for anyone learning the fundamentals of text analysis. Furthermore, you will briefly learn about BERT, part-of-speech tagging, and named entity recognition. Almost 15 different analysis techniques were covered in this course, so chapter 4 ends by recapping all of the great techniques you will learn about in this course.

Exercise 1: Sentiment analysis Exercise 2: tidytext lexicons Exercise 3: Sentiment scores Exercise 4: Sentiment and emotion Exercise 5: Word embeddings Exercise 6: h2o practice Exercise 7: word2vec Exercise 8: Additional NLP analysis Exercise 9: Reviewing methods #1 Exercise 10: Review methods #2 Exercise 11: Conclusion