Questions tagged [libsvm]

LIBSVM is an integrated software library for support vector machines, performing support vector classification, (C-SVC, nu-SVC), regression (epsilon-SVR, nu-SVR) and distribution estimation (one-class SVM)

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Vectors as values in Libsvm format

Is it possible to give an array as a value for libsm features: E.G. 1 1:[2.5,1.4] 2:[1,3.7] 89:[0.93,8.6] Or do we have to only use real values in the values field
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23 views

SVM classification reliability with little data

I'm trying to train an (RBF) SVM model to get a binary classification (1 = class, 0 = no class) based on some features. My dataset is quite small: I have 2500 records for training and 300 for tests. ...
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Will applying SVM in high dimensions (7) with limited training examples (41) likely lead to overfitting?

Right now I have a dataset with 41 training samples (and no testing samples either unfortunately). There are 7 features, but I've been treating the problem as a 2-D problem thus far (in other words, ...
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7 views

(Fast) Feature importance for Support Vector Machine classifier with binary features

I'm dealing with a large dataset: outcome $0$ or $1$, heavily imbalanced with very few $1$'s (~$1\%$) all features are binary, too ($0$ or $1$), and out of $d\approx1000$ features only $s\approx10$ ...
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16 views

Improvements on using factorization machines?

I am fairly new to factorization machines, I have read papers about it and seen examples of it online. My current goal is to solve a recommendation problem and I'm not sure if what I'm doing is ...
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43 views

Coefficients in Optimal Separating Hyperplane(SVM)

This question is closely related to Elements of Statistical Learning p.132 - p.134. I want to reproduce the , in p.129 and p.134, respectively. This is a toy example without given any data, so I ...
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38 views

Recover $\rho$ of $\nu$-SVM from e1071 package in R

Given a dataset $\{(x_i,y_i)\}_{i=1}^n$, the primal problem for $\nu$-SVM is: \begin{align} &\min_{w,b,\xi,\rho} && \frac{1}{2}w^\top w-\nu\rho+\frac{1}{n}\sum_{i=1}^n\xi_i\\ &\text{...
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17 views

SVM favouring one of the two classes

I have a binary classification problem (class 1 and class 0). I need to place the hyperplane such that it avoids ...
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17 views

Why setting SVDD's C-parameter to $> 1$ does not affect the result?

Why setting $C>1$ does not affect the result (compared to $C=1$) according to: https://www.csie.ntu.edu.tw/~cjlin/libsvmtools/#libsvm_for_svdd_and_finding_the_smallest_sphere_containing_all_data ...
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Why LIBSVM provides incorrect accuracy when I am using it with '-b 1'?

I a beginner and trying to explore the libsvm library in MATLAB. I am giving exactly the same data for training and testing using,...
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42 views

Range of Search Space for the hyperparameters of Support Vector Regresssion (SVR)

I need to know "what should be the practical range of c, gamma and epsilon hyper-parameters during grid search optimization in SVR". The range of dependent variable lies between 1 to 300 with mean ...
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231 views

How to perform kFold cross validation in Libsvm's precomputed kernel in MATLAB?

I understand that Libsvm provides 'v 10' option for 10-fold cross-validation in...
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1answer
39 views

Formatting 3d data for LIBSVM

I am going to use LIBSVM for classification of data that uses a 'feature window'. Currently my data is in the form of a M x N x 3 matrix - M instances, N features and for each feature I'm considering ...
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46 views

soft SVM - degenerate case

According to "A Note on Support Vector Machine Degeneracy", Theorem 4, if the dual problem for soft-SVM has a solution with $\alpha_i \in \{0,C\}, \forall i$, then $w=0$ for the primal problem. In "...
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1answer
41 views

SVM decision non linear

As I understand, to perform a decision in a non linear case (using a kernel) I use the following: $f(x) = sgn(\sum_{i=1}^{n} y_{i} \alpha_{i} \boldsymbol{k}(x,x_{i})+b)$ Where i=1,..n are the ...
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2k views

What is the parameter sigma in svm?

What is the influence of the sigma or gamma parameter for the rbf kernel? if possible a graph for a better understanding Is epsilon also known as SIGMA?
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1answer
520 views

What is the parameter nu in oneClass svm?

According to this link, nu specifies the nu parameter for the one-class SVM model. The nu parameter is both a lower bound for the number of samples that are support vectors and an upper bound for the ...
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2answers
85 views

I have 20000 potential features but only 200 instances, how can I do feature selection for an SVM classifier?

I have 20,000 potential features, but only 200 instances, how can I do feature selection for an SVM classifier, especially LIBSVM? Is there any fast way to do it rather than brute force? Since, ...
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27 views

For model selection, using n-fold cross-validation, should performance be averaged over the folds or calculated based on all predictions?

In $n$-fold inner-cross-validation, for model selection, should performance be calculated $n$ times and then averaged, or should all predictions be made covering the whole training set, and then ...
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41 views

When multiple c,g hyper-parameter values yield the same accuracy, how can I choose which c,g is better?

[ Not a duplicate: First of all, my data set is balanced, so accuracy is a reasonable measure of performance. I.e. any value over 50% means that the result is better than random. ] [ Not a duplicate:...
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82 views

Why SVM classifier generates bad results with LDA in Classification of audio data?

I am using SVM classifier to classify my audio data (instrument strokes). I am using LDA as a feature reduction technique to reduce feature dimensions. After applying classifier the results I am ...
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1answer
3k views

What Are Shrinking Heuristics

I have been working on a project with LibSVM and have noticed there is an option to train the SVM model with "shrinking heuristics" which are used to speed up the classifier training. After doing ...
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1answer
31 views

Prepare data for previously trained LibSVM classifier

I trained a LibSVM classifier, with scaled features in the interval $[-1;1]$ with this equation: $$x'=2\frac{x-\min x}{\max x - \min x}-1$$ I am happy with the trained model and its accuracy on the ...
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90 views

One-class svm with given true positive rate

Is it always possible to find a one-class SVM with given true positive rate (TPR)? I used 1-D grid search with cross-validation to find the width parameter of RBF kernel with .90 TPR. The closest ...
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2answers
1k views

(SVM) Difference between linear kernel and polynomial kernel of degree 1?

I am new to machine learning. Could anyone tell me the difference between linear kernel vs. polynomial kernel of degree 1 wrt SVM (if there is any difference)? The reason I asked, I am getting ...
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109 views

Augmenting feature vector with bias in SVM: effect on kernel matrix

It is easier to optimise a SVM without an offset term $b$ since we get rid of one of the linear constraints in the dual formulation. If an offset is still needed, it has been suggested that the ...
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199 views

Optimising dual SVM: why do some authors drop constraints?

In Hastie's Elements of Statistical Learning the dual problem is put as $$ \begin{align} \text{arg min}_\alpha \quad &\ \frac{1}{2}\alpha^\top Q\, \alpha_i- \sum_i \alpha_i\\ \text{subject to}\...
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1answer
98 views

Most widely accepted method of SVM model validation?

I am building an SVM based classifier (libsvm) for two distinct balanced classes which are non-linear but separable with an RBF kernel. Both classes have 175 instances each, which must be utilized ...
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1answer
293 views

what's the more common name of “Three-way data splits”?

I'm using Libsvm to train the model but the result is always not so good. now I'm reading this lecture's document: http://research.cs.tamu.edu/prism/lectures/iss/iss_l13.pdf the lecture mentioned "...
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1answer
525 views

How to use svm for a large dataset to predict

I am using svm method for prediction of wind power using windspeed. I have a large historical dataset containing timestamp, wind speed and wind power of size 6.74MB. it is a one year data at each 5 ...
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610 views

How to apply SVM model to new data using libsvm in MATLAB?

Suppose that I have trained and tested an SVM classifier with the following code: ...
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2answers
5k views

Can someone explain the RBF Kernel to me?

I have read every explanation out there on this but nobody at all seems capable of explaining this very well (either that or I'm utterly stupid). For an SVM RBF Kernel we often say that: But what ...
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1answer
56 views

Why is MSE difference between LIBSVM and my codes?

Now I used LIBSVM toolbox to solve a regression problem. However, I found a question that the value of MSE calculated by the toolbox was different with the value of MSE calculated by myself. Did you ...
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1answer
97 views

bias in SVM in a balanced set - effect of sample size?

I have a dataset with many subjects, and for each subject I have 100 samples for an X variable, while Y has exactly 50%/50% cases for label 1/2. I am trying to run cross-validation with SVM and found ...
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1answer
98 views

Does LibSVM output a broken SVM in epsilon-svr mode?

I run epsilon-svr on about 1000 samples (RBF kernel), and then calculate the in-sample training errors. The hyperparameters are found via a search, ranging from 1e-5 to 1e2. model->eps is a couple ...
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1answer
458 views

Svm-scaling for training and testing using libsvm on matlab [closed]

I want to use SVM-scale for both training and testing on Matlab using libsvm. In libsvm document implement this but using Python and I need for Matlab. how can I do it?
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1answer
503 views

Why all “nBSV”s are zero in LIBSVM classification outputs?

I'm training a classification SVM for a binary classification model with 20 features (LIBSVM). These are some reports of my model (with different combination of features). Why all ...
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1answer
103 views

Do input features need to be in a distribution?

I am currently starting my machine learning project on binary classification and I have been taught that input data features should be in a distribution (although the distribution type itself need not ...
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1answer
83 views

Odd Behavior in Cutoff of Soft Margin SVM

In soft margin svm, we solve the following quadratic programming problem. $$ \text{maximize}\ \sum_{i=1}^N \alpha_i-\sum_{i=1}^N\sum_{j=1}^N\alpha_i\alpha_jy_iy_jX_i^tX_j,\\ \text{subject to}\ \sum_{i=...
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570 views

Standardizing vs Normalizing data for Support Vector Machines

I am fairly new to the topic of Support Vector Machines, and despite my readings, I still encounter difficulties in understanding the following: why do some people address the need to normalize data ...
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106 views

Below chance classification after regressing out class-specific signal

I have a signal X that depends on parameters Y (condition) and S (participant). I'm interested in classifying Y based on X, but a) the YxS contingency table of numbers of observations per Y and S ...
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164 views

Am I correct for cross-validation or validation set in libSVM?

I used libSVM in MATLAB to find whether there is some relationship between the features and label. My steps are: Divide the dataset in 60% for training, 20% for testing and 20% for validation. I used ...
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2answers
827 views

Do SVM suffer from imbalanced class sizes?

Say I have a population with classes c1 and c2 where size(c1) >> size(c2) Does the SVM suffer from imbalanced classes sizes where I need to manually correct the training procedure?
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251 views

How to use Probability (-b1) for one-class classification using LibSVM?

I need some information concerning the LibSVM one-class classification. I use -b1 for two-class classification in SvmTrain and my outputs are prob values and prob labels. I want to use the similar ...
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1answer
694 views

How to train an SVR model? [closed]

I'm trying to figure out how SVR works, as I need to use it to model some time series. For this purpose, before starting with this model, I've tried to create a toy-model from a sinusoidal function, ...
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1answer
480 views

Training a Support Vector Machine classifier on a satellite image using python

I am new to the concept of supervised classification technique. I am trying to use an SVM classifier for classifying Sea Ice types in the Arctic using satellite image. All the tutorials I have read ...
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1answer
197 views

One-to-rest Weight vectors in one-to-one multiclass SVC

I'm attempting to generate some one-to-rest weight vectors for a multi-class SVC for feature selection purposes. However, I'm current using one of the several LibSVM ports, which inherently performs ...
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1answer
156 views

Using LibSVM for One-Class-Classification

Why do the same instances, in training and testing, get classified as unknown in LibSVM? I'm using the linear kernel function nu=0.1, gamma=0.1 Here is the instance that is in both the training and ...
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1answer
4k views

SVM: Why does the number of support vectors decrease when C is increased?

I am learning how to use libsvm through sklearn.svm in python. I read here about what happens and why when you change the C value as part of your model. My intuition from what I've learned would be ...
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202 views

Using SVM regression model without cross-validation and parameter optimization

I am working on a regression model of quite complicated dataset. Dataset is heterogenous in the sense that it contains elements of significantly different properties. I am using $\epsilon$ type ...