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Mastering Machine Learning with R

You're reading from   Mastering Machine Learning with R Advanced machine learning techniques for building smart applications with R 3.5

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Product type Paperback
Published in Jan 2019
Publisher
ISBN-13 9781789618006
Length 354 pages
Edition 3rd Edition
Languages
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Author (1):
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Cory Lesmeister Cory Lesmeister
Author Profile Icon Cory Lesmeister
Cory Lesmeister
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Toc

Table of Contents (16) Chapters Close

Preface 1. Preparing and Understanding Data 2. Linear Regression FREE CHAPTER 3. Logistic Regression 4. Advanced Feature Selection in Linear Models 5. K-Nearest Neighbors and Support Vector Machines 6. Tree-Based Classification 7. Neural Networks and Deep Learning 8. Creating Ensembles and Multiclass Methods 9. Cluster Analysis 10. Principal Component Analysis 11. Association Analysis 12. Time Series and Causality 13. Text Mining 14. Creating a Package 15. Other Books You May Enjoy

N-grams

Looking at combinations of words in, say, bigrams or trigrams can help you understand relationships between words. Using tidy methods again, we'll create bigrams and learn about those relationships to extract insights from the text. I will continue with the subject of President Lincoln as that will allow you to compare what you gain with n-grams versus just words. Getting started is easy, as you just specify the number of words to join. Notice in the following code that I maintain word capitalization:

> sotu_bigrams <- sotu_meta %>%
dplyr::filter(year > 1860 & year < 1865) %>%
tidytext::unnest_tokens(bigram, text, token = "ngrams", n = 2,
to_lower = FALSE)

Let's take a look at this:

> sotu_bigrams %>%
dplyr::count(bigram, sort = TRUE)
# A tibble: 17,687 x 2
bigram n
<chr> <int>
1 of the...
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