Tagged Questions

1
vote
1answer
80 views

When does Naive Bayes perform better than SVM?

In a small text classification problem I was looking at, Naive Bayes has been exhibiting a performance similar to or greater than an SVM and I was very confused. I was wondering what factors decide ...
1
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2answers
48 views

How can I use Bayes rule for this question given additional data

I am required to use the Naive Bayes classifier to classify example 8, to see whether it is poisonous or not. I gained the following results: p(x|Poisonous=Y) = 0.0267857 and p(x|Poisonous=N) = ...
0
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0answers
60 views

How to solve this problem using Bayes Rule?

I have become stuck on answering question 1c, which requires me to: use the Bayes rule with the naive Bayes Assumption. I understand how to use the naive Bayes classifier but not using the assumption. ...
0
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0answers
28 views

Can very large numbers of samples throw off Naive Bayes?

I'm writing what is effectively a spam filtering system. I have about three million samples, mostly bag-of-words and top-tfidf based samples, and I'm seeing abysmal precision and recall. I'm trying to ...
0
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0answers
54 views

Forming training set for Multinomial Naive Bayes

Is it true that Multinomial Naive Bayes requires equally by count training data for each class to get best performance? For example, we forming classifier for three classes - Japan, China, Korea. ...
0
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0answers
80 views

Mixing categorial and continuous data in Naive Bayes classifier using scikit-learn

I'm using scikit-learn in Python to develop a classification algorithm to predict gender of a certain customers. Amongst others I want to use the Naive Bayes classifier but my problem is that I have a ...
2
votes
1answer
206 views

Decision threshold for a 3-class Naive Bayes ROC curve

I have some doubts regarding how a ROC curve for a 3-class classifier (Naive Bayes) can be built. Basically, given some test data, the classifier outputs the probabilities for each of the 3 possible ...
3
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1answer
354 views

Naive Bayes fails with a perfect predictor

Let's say I have a variable that perfectly predicts one of the classes in my dataset: ...
2
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0answers
99 views

How to choose the distribution and parameters for continuous probability density functions in naive Bayes using maximum likelihood?

Let's assume I want to train a binary naive Bayes classifier, with classes $y_0, y_1$ and $n$-dimensional data. For this one needs to calculate the conditional probabilities $P(x_i | y_j) $ for all ...
0
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0answers
49 views

Generating a quality score

Let's say that I am buying something, let's say it's information on consumers. I am bidding on an item and could win or not win. If I win an item, and realize that what I purchased was of poor ...
2
votes
1answer
129 views

Including missing words when applying Naive Bayes in document classification

When applying a naive Bayes classifier to document classification, the classifier (at least in the applications I've seen) always iterates only over the words actually present in the document. That ...
3
votes
1answer
383 views

Why does my naive Bayes classifier only give me probabilities near 0?

I'm building a text classifier using the naive Bayes formula. I'm still early in the development, but I already see a problem with my technique and I was wondering if you guys would have idea that ...
2
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0answers
136 views

Regarding kernel-based naive Bayesian classifier

Are there any good references for kernel-based Naive Bayesian classifier?
0
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0answers
223 views

Multi Class vs 2 class Naive Bayes

I was wondering what are the implications of using a multi-class Naive Bayes versus a 2 class Naive Bayes (for one against everything). Which technique performs better? I've previously came across ...
2
votes
0answers
334 views

Adjusting the classification threshold of Naive Bayes

I've been involved in a machine learning project recently and am now in the process of writing the project up for a paper submission. We used the naive bayes classifier on the project and developed a ...
1
vote
1answer
158 views

Feature selection weighting 2 filters in Naive Bayes

I am trying to do text classification using Naive Bayes. Before training, I would like to make feature selection in order to reduce the feature space dimension. In order to do so, I have thought of ...
2
votes
1answer
240 views

Naive Bayes for two continuous features

I have two features which are both continuous. How to perform a classification task based on them? I've read the Wikipedia entry on Naive Bayes, but this is only for discrete outcome and one feature.
12
votes
3answers
838 views

Understanding Naive Bayes

To demonstrate the concept of Naïve Bayes Classification, consider the example displayed in the illustration above. As indicated, the objects can be classified as either GREEN or RED. My task is to ...
4
votes
2answers
237 views

How are classifications merged in an ensemble classifier?

How does an ensemble classifier merge the predictions of its constituent classifiers? I'm having difficulty finding a clear description. In some code examples I've found, the ensemble just averages ...
5
votes
1answer
503 views

TF-IDF cutoff percentage for tweets

I'm currently trying to analyze Tweets and classify them as either positive, negative, or neutral using the NLTK library in Python. I can see that there's potential in the approach that I'm taking, ...
5
votes
2answers
405 views

Naive-Bayes classifier for unequal groups

I'm using naive bayes classifier to classify between two groups of data. One group of the data is much larger than the other (above 4 times). I'm using the prior probability of each group in the ...
5
votes
2answers
1k views

Increasing number of features results in accuracy drop but prec/recall increase

I am new to Machine Learning. At the moment I am using a Naive Bayes (NB) classifier to classify small texts in 3 classes as positive, negative or neutral, using NLTK and python. After conducting ...
0
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0answers
69 views

What is the appropriate method to use to calculate customer lifetime value?

I'd like to figure out what the potential lifetime value of a customer may be based on their purchasing patterns with our products. I have transactional data that tells me what a customer purchased, ...
5
votes
3answers
815 views

Naive Bayes classification for “That's what she said” problem

I became interested in doing this in C# for my own amusement after reading the following papers: http://www.cs.washington.edu/homes/brun/pubs/pubs/Kiddon11.pdf I also took a look at ...
0
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0answers
662 views

How to convert log likelihoods into scores in Naive Bayes?

I am currently implementing a text classification program with Naive Bayes. I produce two multinominal models in my training function: p(w|nonSPAM) and p(w|SPAM)) as well as a prior probability P(S). ...
5
votes
2answers
325 views

Overfit by removing misclassified objects?

Actually this question may be simple for you, but I need to learn the correct answer. If I remove misclassified instances from data set with Naive Bayes (it gives minimum FP rate) and then train ...
2
votes
1answer
678 views

Bayesian classifier with multivariate normal densities

Supposing a Bayesian classifier with multivariate normal densities, how do I find the error rate of the classifier when we have two classes? I am using this: When dimension $d = 1$: $$P(x | \mu , ...
1
vote
1answer
252 views

Bayes classifier

Given the prior probability of 2 distributions, $N(x,y)$ and $N(a,b)$, where $N(\mu,\sigma^2)$: How do you make a decision rule to minimize the probability of error, if the prior probabilities are ...
9
votes
2answers
5k views

Akinator.com and Naive Bayes classifier

Context: I am a programmer with some (half-forgotten) experience in statistics from uni courses. Recently I stumbled upon http://akinator.com and spent some time trying to make it fail. And who ...
4
votes
1answer
205 views

Factored Joint Distribution of Tree Augmented Naive Bayes Algorithm

I asked this question at Mathoverflow but they recommend me to ask here. I need to find factored joint distribution of Tree Augmented Naive Bayes algorithm. I read the paper but I couldn't figure out ...
2
votes
1answer
678 views

MLE for Naive Bayes in R

I am using the naivebayes function of the e1071 library. Some example commands are: ...