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35 views

VW multiclass classification

I am new to vw and trying to do a multiclass text classification with 18 classes. features are unigram, bigram and trigrams. Total features are around 1.4 million Total training examples 35 million ...
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2answers
63 views

Output of Scikit SVM in multiclass classification always gives same label

I am currently using Scikit learn with the following code: ...
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0answers
11 views

Is it OK to resample data in one vs all multiclass classification?

I have a multiclass classification problem and decide to use one vs all logistic regression. Since some classes are very rare (pos vs neg is like 1:100), I plan to use some balancing strategy during ...
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0answers
6 views

Classification under uncertainty in observations

I am tackling a multiclass classification problem where the values of the independent variables are not known with certainty. Instead, each observation is represented by a multivariate Gaussian pdf ...
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0answers
12 views

Do you know about SVM plait?

I need to know about how I can applied many single SVMs? because I have read about SVM plait that does this kind of classifications that is using many single SVMs to improve the classification process ...
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0answers
18 views

LibSVM totalSV for multiclass

I am performing classification of K=9 classes using linear SVM with libSVM (MATLAB warp) I am using 400 samples of data to perform the training and I'm getting: totalSV: 203 I know libSVM uses ...
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0answers
28 views

dealing with imbalanced data set in multiclass text classification

I need to build a text classification model. I have a labeled training set and my goal is to classify the new unlabeled text . My training set is composed on 6 categories, that are imbalanced. The ...
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1answer
133 views

Suggestions needed about classifier fusion

I'm working on a classification problem which involves two classifier to observe a single event. I'm providing a high level description of the problem without going into the technical details (the ...
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0answers
9 views

Multiclass target detection : N X (1 vs all) or 1 X (N vs all) ?

I am doing a multiclass classification using neural networks. say I have 10 target classes and one null (non-of-the-above-targets). is it better that I train a neural network separately for each ...
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1answer
51 views

About grid search to find the best value of C

I know when I want to find the best values of C and gamma, I should use grid-search. But in my case I want to find just the best value of C. So, this is called a line-search. Is there any function ...
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0answers
14 views

Assign attributes / categories to users based on their activity / likes

I have a very practical classification problem for which I need some help. I have a database of users along with their activity / likes for a number of car models. I also have the category each of ...
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0answers
76 views

Multi-class logarithmic loss function per class

In a multi-classification problem, we define the logarithmic loss function $F$ in terms of the logarithmic loss function per label $F_i$ as: $$ F = -\frac{1}{N}\sum_{i}^{N}\sum_{j}^{M}y_{ij} \cdot ...
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0answers
3 views

How can I counteract the effect of a degenerate classifier in an OVA Model?

Suppose I build a OVA classification model for classification with more than 2 possible classes (a model of sub-models, where each submodel predicts the probability of a data point belonging in a ...
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0answers
13 views

Implementation of batch Hieron

I would like to implement the Hieron algorithm, which is described in the paper "Large Margin Hierarchical Classification". The basic online Hieron is specified in the paper, but I need the batch ...
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0answers
70 views

Multi-class AUC in Matlab

I would like to compute the area under the ROC-courve (AUC) metric for a classifier with multiple classes. Do you know (reliable) functions for Matlab that implement methods for that, like e.g. in ...
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0answers
25 views

Walking recognition

I have walking samples from 20 different people. My aim is to detect which walking samples are from which person. I'm trying to achieve this by extracting "walking cycles" from each person's dataset ...
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0answers
134 views

Logistic regression with multi-class features in R

I'm working with a data set like the following: X = ...
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0answers
62 views

Softmax regression or $K$ binary logistic regression

For a multi-class classification problem, we can use $K$ binary logistic classifiers, or one softmax regression classifier, so how to make the choice between the two? IMHO, the $K$ binary logistic ...
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1answer
146 views

What is the difference between a multi-label and a multi-class classification?

What is the difference between multi-label classification and multiclass classfication. Speficially, what is the difference between a label and a class? Please provide a clear example. "Multiclass ...
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1answer
347 views

How to get confidence on classification predictions with multi-class Vowpal Wabbit

I have a classification problem in which I'm using the --ect option for the multi-class algorithm. The output of the classifier is something as follows: ...
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0answers
18 views

Quality of NER classification decreases dramatically when sliding window transformation is performed

I'm writing a NER classificator now. That performs quite well even without window transformation (~80% F1-score for non-English language is quite well, AFAIK), but the strange thing is that when I ...
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0answers
92 views

What should I use - Multi label classification or Multi class classification? [duplicate]

In my dataset, I have 2 labels, positive and negative. Most samples belong to only one class, either positive or negative. A small fraction of samples take both labels i.e. both positive and negative. ...
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0answers
65 views

Popular implementations of one vs all logistic regression for mutiple classes in R

Is there any popular implementation of logistic regression in R that defaults to using a one vs all approach for a categorical dependent variable with more than two classes? I have specific reasons to ...
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0answers
11 views

Precision of an incomplete classifier

Given a testing set of nodes which can be either +,-, or 0, I use an incomplete classifier which allows me to predict if a node is +, -, 0, not +, not -, or not 0, and sometimes it cannot predict ...
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2answers
59 views

Can a nuisance multi-class classifier do better than binary classifier?

This is rather a theoretical question in order to save the trouble in trying to do empirical testing and is part of a bet, so I hope I am right... Say there are M classes in the data BUT you want to ...
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0answers
30 views

How to extract the weight and bias in libsvm?

I want to extract the weight and the bias for my dataset which has two columns and more than 3000 rows. Also I want to draw a line by this equation: y = w.x + b where w is the weight, x is the data ...
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1answer
135 views

What is the difference between accuracy and agreement?

According to Manning et al. (p. 155) accuracy is the sum of the diagonal in the confusion matrix divided by the sum of all items. On the other hand, following Artstein and Poesio (p . 558) precisely ...
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0answers
30 views

Implementing MMAC algorithm

I was reading a paper by Fadi A. Thabtah and et al., "MMAC: A New Multi-class, Multi-label Associative Classification Approach". I was trying to implement their MMAC algorithm. In MMAC algorithm that ...
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0answers
71 views

Significance test for multiclass classifier

In a multiclass classification problem, I want to measure the significance of my classifier against the null hypothesis (in this case, chance level). In this paper, in section 3.4, for a binary ...
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1answer
41 views

Limit multiclassification SVM - ANN

I have some questions on the limits of SVM and ANN for multiclass problem. I know about "one vs all" and "all vs all" strategies but I only want to know the limit of a unique SVM and ANN. Is there a ...
1
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1answer
137 views

Linear statistical model with two-class variables

Suppose I have a set of (discrete) variables, say $X_1,\dots,X_n$. Each $i$ belongs to either class A or class B. When it belongs to A the contribution is $Y_{A,i}f(X_i)$, and when it belongs to B the ...
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0answers
43 views

Learning from distance matrices

I have a task to build multi-task classification model based on distance (similarity) matrix only. They are already precalculated and no changes here can be applied. Can you, please, recommend me ...
3
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1answer
79 views

libsvm_linear kernel_increasing C value

I'm using libsvm in C-SVC mode (-s= 0) with linear kernel (-t= 0), and I'm required to train multiple SVMs( I have four classes). My training and test sets have the same number of instances and ...
2
votes
1answer
307 views

Using predict_proba with sklearn's multiclass SVC

I'm using python's sklearn for multi-class classification (SVC) When using the predict method, i get very high scores with my dataset, However, I want to plot ROC curves for each of my classes. That ...
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0answers
59 views

Decompose LibSVM model into binary classifiers

I have a multi-class .model trained with LibSVM. Is there a way to decompose this model into different binary .model files? For example, if I have a .model trained for $n$ classes, I would like to ...
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3answers
61 views

“finely” labeled classification problem

I came across a kind of classification problem. Suppose I have a dataset with labels, where each label is one of a1, a2, a3, b1, and b2. I want to make a classifier that estimates "coarse" label, a ...
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2answers
138 views

Good strategy for multiclass classification (when there is hierarchical class structure )

Combining binary classifiers, I want to solve multi-class classification problem in the following setting. Suppose there is a dataset and each data is in one of four classes: A1, A2, B1 and B2. A1 and ...
2
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1answer
165 views

Area Under ROC Curve for Multiple Classes

I am working with a highly class-skewed three class classification problem. The class percentages are A = 1.8%, B = 17.5% and C = 80.7%. According to this paper, the following definition of ...
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1answer
161 views

Unassigned classes in Multiclass SVM with One vs All Approach

How do you handle unassigned classes in multiclass support vector machines (multiclass SVM) with the One vs All approach? Lets say my training data has three classes A, B, and C. I use 3 SVM ...
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1answer
75 views

Transform multiclass classification to binary - benefits?

I have 400 instances which must be categorized into 4 classes. Using WEKA, I tried out a couple of multiclass classifiers like J48 and Random Forests, but never made it above Kappa 0.6 and ~65% ...
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0answers
324 views

Divison of multi class into binary class using libsvm (not classification)

I am working on multi class imbalance data.I want to divide my classes based on one verus one method and then perform sampling techinque How can I do that I just want to divide the classes not ...
3
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2answers
156 views

Machine learning for multi-level response

I have a dataset with ~90000 observations and less than 10 features (all continuous). The problem is that the response variable has ~300 categories. Currently I would try to fit a multinomial linear ...
6
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1answer
3k views

How to use scikit-learn's cross validation functions on multi-label classifiers

I'm testing different classifiers on a data set where there are 5 classes and each instance can belong to one or more of these classes, so I'm using scikit-learn's multi-label classifiers, ...
0
votes
1answer
219 views

How to improve classification performance based on multiple known classification results

I am working on a classification problem, which may contains a unknown number of data classes, typically 5-50 classes in each sample. I had several classification algorithms, each gives me a ...
2
votes
1answer
181 views

Hierarchical classification where leaf nodes in a tree are at no particular level

I have a set of hierarchical classes (ex. "object/architecture/building/residential building/house/farmhouse"), and I build a tree where each node is a classifier. However, the appropriate class for a ...
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2answers
589 views

How can a multiclass perceptron work?

I don't have any background in math, but I understand how the simple Perceptron works and I think I grasp the concept of a hyperplane (I imagine it geometrically as a plane in 3D space which seperates ...
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2answers
3k views

libSVM - probability estimates in multi-class problems

I am using libSVM for classification on a 3-class dataset. Using the option "-b 1" - for getting probability estimates for prediction - gives me surprising results. I am reproducing the issue with a ...
3
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2answers
290 views

Named entity recognition and class imbalance

I have implemented Maximum-entropy Markov model (MEMM) for the Named entity recognition (NER) problem. I have four classes: geographical, people, material (book titles etc) and other. Class ...
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0answers
293 views

Maximum number of classes for RandomForest multiclass estimation

I have researched the internet|literature a lot on multiclass prediction to find out what is a realistic limit for the number of classes that can successfully be used for estimation when using a ...
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1answer
470 views

Confusion matrices with percentages rather than number of instances?

Most of the confusion matrices I've seen contain the number of instances in each cell. Isn't a confusion matrix with the percentage of instances in each cell easier to read? Is this approach wrong or ...