Naive-Bayes - Part 1

Some very basic ML using Naive-Bayes and the tidymodel framework.

library(readr)
library(dplyr)  # mutate(), row_number()

df <- read_csv('../../../raw_data/financial_news.csv', col_names = c('sentiment', 'text')) |> 
  mutate(sentiment = factor(sentiment))

Using the tidyverse, we’ll

• split the df into a training and testing set.

library(rsample)    # initial_split(), training(), testing()
library(recipes)
library(parsnip)    # naive_bayes(), set_engine()
library(workflows)  # workflow()

library(discrim)
library(textrecipes)
library(yardstick)

list_splits <- initial_split(df, prop = 0.8, strata = 'sentiment')
df_train <- training(list_splits)
df_test <- testing(list_splits)

list_recipe <- recipe(sentiment ~., data = df_train) |> 
  step_tokenize(text) |> 
  step_stopwords(text) |> 
  step_tokenfilter(text, max_tokens = 100) |> 
  step_tfidf(text)
  

mod_nb <- naive_Bayes() |> set_engine('naivebayes') |> set_mode('classification')
mod_svm <- svm_poly() |> set_engine('kernlab') |> set_mode('classification')
list_cv <- vfold_cv(df_train, v = 5, strata = 'sentiment')

wf_nb <- workflow() |> add_recipe(list_recipe) |> add_model(mod_nb)
wf_nb

══ Workflow ════════════════════════════════════════════════════════════════════
Preprocessor: Recipe
Model: naive_Bayes()

── Preprocessor ────────────────────────────────────────────────────────────────
4 Recipe Steps

• step_tokenize()
• step_stopwords()
• step_tokenfilter()
• step_tfidf()

── Model ───────────────────────────────────────────────────────────────────────
Naive Bayes Model Specification (classification)

Computational engine: naivebayes 

wf_svm <- workflow() |> add_recipe(list_recipe) |> add_model(mod_svm)

fit_mod_nb <- fit(wf_nb, df_train)
pred_mod_nb <- predict(fit_mod_nb, df_test)
pred_mod_nb_prob <- predict(fit_mod_nb, df_test, type = 'prob')

fit_mod_svm <- fit(wf_svm, df_train)

 Setting default kernel parameters  

pred_mod_svm <- predict(fit_mod_svm, df_test)
pred_mod_svm_prob <- predict(fit_mod_svm, df_test, type = 'prob')

bind_cols(df_test, pred_mod_nb) |> conf_mat(sentiment, .pred_class)

          Truth
Prediction negative neutral positive
  negative       36      22       44
  neutral        74     531      188
  positive       11      23       41

bind_cols(df_test, pred_mod_svm) |> conf_mat(sentiment, .pred_class)

          Truth
Prediction negative neutral positive
  negative       22      12       22
  neutral        81     540      183
  positive       18      24       68

#roc_nb <- bind_cols(df_test, pred_mod_nb_prob) |> roc_curve()