Lab 06 - Text Mining

January 1, 0001 
knitr::opts_chunk$set(eval = FALSE, include  = TRUE)

Learning goals

  • Use unnest_tokens() and unnest_ngrams() to extract tokens and ngrams from text.
  • Use dplyr and ggplot2 to analyze text data

Lab description

For this lab we will be working with a new dataset. The dataset contains transcription samples from https://www.mtsamples.com/. And is loaded and “fairly” cleaned at https://raw.githubusercontent.com/USCbiostats/data-science-data/master/00_mtsamples/mtsamples.csv.

Setup packages

You should load in dplyr, (or data.table if you want to work that way), ggplot2 and tidytext. If you don’t already have tidytext then you can install with

install.packages("tidytext")

read in Medical Transcriptions

Loading in reference transcription samples from https://www.mtsamples.com/

library(readr)
library(dplyr)
mt_samples <- read_csv("https://raw.githubusercontent.com/USCbiostats/data-science-data/master/00_mtsamples/mtsamples.csv")
mt_samples <- mt_samples %>%
  select(description, medical_specialty, transcription)

head(mt_samples)

Question 1: What specialties do we have?

We can use count() from dplyr to figure out how many different catagories do we have? Are these catagories related? overlapping? evenly distributed?

mt_samples %>%
  count(___, sort = TRUE)

Question 2

  • Tokenize the the words in the transcription column
  • Count the number of times each token appears
  • Visualize the top 20 most frequent words

Explain what we see from this result. Does it makes sense? What insights (if any) do we get?

Question 3

  • Redo visualization but remove stopwords before
  • Bonus points if you remove numbers as well

What do we see know that we have removed stop words? Does it give us a better idea of what the text is about?

Question 4

repeat question 2, but this time tokenize into bi-grams. how does the result change if you look at tri-grams?

Question 5

Using the results you got from questions 4. Pick a word and count the words that appears after and before it.

Question 6

Which words are most used in each of the specialties. you can use group_by() and top_n() from dplyr to have the calculations be done within each specialty. Remember to remove stopwords. How about the most 5 used words?

Question 7 - extra

Find your own insight in the data:

Ideas:

  • Interesting ngrams
  • See if certain words are used more in some specialties then others