# Questions tagged [naive-bayes]

For questions related to the naive Bayes, which is a machine learning (or statistics) technique that is based on the Bayes' theorem.

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### Why do I get small probabilities when implementing a multinomial naive Bayes text classification model?

When applying multinomial Naive Bayes text classification, I get very small probabilities (around $10e^{-48}$), so there's no way for me to know which classes are valid predictions and which ones are ...
421 views

### Why is the denominator ignored in the Bayes' rule?

The naïve Bayes' generative algorithm is often represented by the following formula: $$\text{argmax}_{y} p(y|x) = \text{argmax}_y \frac{p(x|y)p(y)}{p(x)} \approx \text{argmax}_y p(x|y)p(y)$$ Why do we ...
12 views

### How to add pseudocounts to naive Bayes classifier?

I'm trying classify a document containing words $[x_i...x_n]$ as spam or non-spam, using this equation from Wikipedia: $$p(spam|x_i,...,x_n) = p(spam)\prod^n_{i=1}p(x_i|spam)$$ But I'm confused about ...
63 views

### How can I apply naive Bayes classifier for three classes (Positive, Negative and Neutral) in text data?

I found a naive Bayes classifier for positive sentiment or a negative sentiment Citius: A Naive-Bayes Strategy for Sentiment Analysis on English Tweets. But with most available datasets online, ...
2k views

### What are the main differences between a perceptron and a naive Bayes classifier?

What are the main differences between a perceptron and a naive Bayes classifier?
186 views

### What to do when PDFs are not Gaussian/Normal in Naive Bayes Classifier

While analyzing the data for a given problem set, I came across a few distributions which are not Gaussian in nature. They are not even uniform or Gamma distributions(so that I can write a function, ...
91 views

### $\frac{P(x_1 \mid y, s = 1) \dots P(x_n \mid y, s = 1) P(y \mid s = 1)}{P(x \mid s = 1)}$ indicates that naive Bayes learners are global learners?

I am currently studying the paper Learning and Evaluating Classifiers under Sample Selection Bias by Bianca Zadrozny. In section 3. Learning under sample selection bias, the author says the following: ...
11 views

### How to make specific test data prediction with fitted GaussianNB Classifier in Python

I'm trying to make news classification. Here is the neural network: ...
23 views

### Why don't ensembling, bagging and boosting help to improve accuracy of Naive bayes classifier?

You might think to apply some classifier combination techniques like ensembling, bagging and boosting but these methods would not help. Actually, “ensembling, boosting, bagging” won’t help since their ...
21 views

### Are there any examples of state-of-the-art NLP applications that are still n-gram based and use Naive Bayes?

As far as I can tell, most NLP tasks today use word embeddings and recurrent networks or transformers. Are there any examples of state-of-the-art NLP applications that are still n-gram based and use ...
40 views

### How can the expectation-maximization improve the classification?

I am learning the expectation-maximization algorithm from the article Semi-Supervised Text Classification Using EM. The algorithm is very interesting. However, the algorithm looks like doing a ...
64 views

### Understanding how to calculate $P(x|c_k)$ for the Bernoulli naïve Bayes classifier

I'm looking at the Bernoulli naïve Bayes classifier on Wikipedia and I understand Bayes theorem along with Gaussian naïve Bayes, however when looking at how $P(x|c_k)$ is calculated I don't understand ...