3
votes
1answer
81 views

Machine learning techniques for spam detection, and in general for text classification

I am going to configure a system for spam detection. What I have is a dataset of labeled (spam/not-spam) strings containing, mostly, sentences. I have a background in machine learning techniques, but ...
1
vote
0answers
41 views

Exploratory Analysis - finding the most important factor

I have a dataset of 113 variables. In exploratory analysis the first thing I want to know is what are the most important factors on a single variable (revenue). I learned that naive Bayes would ...
1
vote
1answer
43 views

Simple question about multivariate/multiclass classification

From this link Text Classification using Naive Bayes, there are two models described for classification, Naive and Bernoulli. My question is if i want to make this classifiers for multiclass ...
1
vote
1answer
191 views

Logistic Regression\SVM implementation in Mahout

I am currently working on sentimental analysis of twitter data for one of telecom company data.I am loading the data into HDFS and using Mahout's Naive Bayes Classifier for predicting the sentiments ...
1
vote
0answers
72 views

Sentimental Analysis using Naive Bayes

I am working on problem solution where I am collecting social feeds from twitter and Facebook for a product X . I am labeling these posts,comments or tweets using five labels ...
0
votes
1answer
44 views

Bayesian Classification evaluation

I am trying to implement Bayesian Classification on the data set as follows: "Problem: classify whether a given person is a male or a female based on the measured features. The features include ...
-2
votes
2answers
99 views

Naive Bayes model [duplicate]

i am trying to implement the naive bayes algorithm in java. But i have a few confusions on the naive bayes model. What is the model of naive bayes? Is it a table ?how we can make prediction from the ...
1
vote
0answers
125 views

Predicting Naive Bayes model in R on a test data with a single record

I built a naivebayes model using the Housevotes84 data(discrete data) in mlbench package- model <- naiveBayes(Class~., data=HouseVotes84) I took one record ...
2
votes
3answers
145 views

Machine Learning to Predict Class Probabilities

I am looking for classifiers that output probabilties that examples belong to one of two classes. I know of logistic regression and naive Bayes, but can you tell me of others that work in a similar ...
1
vote
1answer
226 views

Prediction using Naive Bayes of klaR package fails

I am trying to replicate a example that I found in Tom Mitchell's book Machine Learning (1997), using R. It is a example from chapter 6. There are 14 training examples (shown below) of the target ...
1
vote
1answer
89 views

Sentiment Analysis with respect to subject

I'm familiar with the bag of words/Naive bayes sentiment analysis for text (e.g. http://streamhacker.com/2010/05/10/text-classification-sentiment-analysis-naive-bayes-classifier/) I was curious to ...
2
votes
1answer
86 views

Naive Bayesian class probability greater than one

I have a problem with a simple Naive Bayes calculation. Given that I have an inbox, with the following characteristics: The mailbox contains 100 emails 50 emails contain the word “money”. 30 emails ...
1
vote
2answers
67 views

Equal number of training instances of each classification label?

I am using Naive Bayes to perform binary classification. In my training set, the two class labels occur with probability Pr(label A) = 0.95 and Pr(label B) = 0.05. Should I prune the training set so ...
0
votes
1answer
75 views

Trouble reading multinomial naive bayes notation

$C_{MAP}$: most likely class (i.e., "maximum a posteriori") $C_{NB}$: Naive Bayes x: document d is represented as $x_n$ ...
3
votes
1answer
2k 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
vote
3answers
98 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
votes
0answers
83 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
votes
0answers
77 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. ...
2
votes
1answer
353 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
votes
1answer
688 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
votes
0answers
120 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
votes
0answers
59 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
206 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 ...
4
votes
1answer
841 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
votes
0answers
253 views

Regarding kernel-based naive Bayesian classifier

Are there any good references for kernel-based Naive Bayesian classifier?
0
votes
0answers
445 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
575 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
204 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
422 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.
18
votes
3answers
1k 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 ...
6
votes
2answers
332 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
755 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, ...
6
votes
2answers
765 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 ...
6
votes
2answers
2k 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
votes
0answers
101 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, ...
6
votes
3answers
991 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
votes
0answers
962 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). ...
6
votes
2answers
421 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
1k 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
306 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 ...
10
votes
2answers
6k 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
230 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
758 views

MLE for Naive Bayes in R

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