Naive Bayes Classifier in Python | Naive Bayes Algorithm | Machine Learning Algorithm | Edureka

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Naive Bayes

Today’s Training Topics
❖ What is Naïve Bayes?
❖ Bayes Theorem and it’s Use
❖ Mathematical working of Naïve Bayes
❖ Step by Step Programming Naïve Bayes
❖ Prediction using Naïve Bayes

What is Naïve Bayes ?

What is Naïve Bayes ?
Naive Bayes is a simple but surprisingly powerful algorithm
for predictive modeling.
Bayes

Bayes’ Theorem
Given a hypothesis H and evidence E , Bayes' theorem states
that the relationship between the probability of the hypothesis
before getting the evidence P(H) and the probability of the
hypothesis after getting the evidence P(H|E) is
P(H|E) = P(E|H).P(H)
P(E)

Bayes’ Theorem Example

P(King) = 4/52 =1/13

P(King) = 4/52 =1/13
P(King|Face) = P(Face|King).P(King)
P(Face)

P(King) = 4/52 =1/13
P(Face)
P(Face|King) = 1

P(King) = 4/52 =1/13
P(Face)
P(Face|King) = 1
P(Face) =12/52 = 3/13

P(King) = 4/52 =1/13
P(Face)
= 1.(1/13) = 1/3
3/13
P(Face|King) = 1
P(Face) =12/52 = 3/13

Bayes’ Theorem Proof
P(H|E) = P(E|H).P(H)
P(E)
Likelihood
How probable is the evidence
Given that our hypothesis is true?
Posterior
How probable is our Hypothesis
Given the observed evidence?
(Not directly computable)
Prior
How probable was our hypothesis
Before observing the evidence?
Marginal
How probable is the new evidence
Under all possible hypothesis?

Naïve Bayes: Working
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Classification Steps

Industrial Use Of Naïve Bayes

National
International
Sports
Media
Stock Market
Politics
Finance
Travel & Lifestyle
NEWS
Categorization

SPAM
Filtering

OBJECT
&
FACE
Recognition

MEDICAL
Diagnosis

WEATHER
Prediction

Types of Naïve Bayes
Gaussian
Multinomial
Bernoulli

Steps Involved in Naïve Bayes

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Step1: Handling Data

Step2: Summarizing Data

Step3: Making A Prediction

Step4: Making All the Predictions

Step5: Evaluate Accuracy

Step6: Tying all Together

Naive Bayes Classifier in Python | Naive Bayes Algorithm | Machine Learning Algorithm | Edureka

Naive Bayes Classifier in Python | Naive Bayes Algorithm | Machine Learning Algorithm | Edureka

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Naive Bayes Classifier in Python | Naive Bayes Algorithm | Machine Learning Algorithm | Edureka