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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55 views

What are the weights assigned to the features (coefficients in the primal problem) in SVR? [closed]

In case of linear kernel, how to interpret the weights in the formulations of nu-SVR? I am using nu-SVR to estimate the parameters in GARCH(1,1) model:$ \sigma_t^2 = \omega + \alpha y_{t-1}^2 + \...
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25 views

hinge loss functions in SVM

Hi as I am writing report regarding the topic SVM and I have to elaborate on the differences between SVC and linearSVC in Scikit Learn, I search online that the two algorithms differ in terms of hinge ...
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26 views

sklearn SVC never ending training, features extracted from VGG16

SVC is based on libsvm. When I train SVM with a small image dataset the training finishes but for a large image dataset not converging even after 11 hours on GPU server. ...
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12 views

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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25 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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18 views

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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20 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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25 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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85 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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53 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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19 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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1answer
34 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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56 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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1answer
341 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
46 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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60 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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2answers
4k 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
960 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
98 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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0answers
30 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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42 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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87 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
37 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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94 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
2k 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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137 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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218 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
134 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
382 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
603 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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1answer
677 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
6k views

Can someone explain the RBF Kernel to me?

I have read every explanation out there on this but nobody seems capable of explaining this in a way that I am able to understand. For an SVM RBF Kernel we often say that: But what does x and x' ...
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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
103 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
104 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
520 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
550 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
124 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
86 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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0answers
660 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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0answers
117 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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0answers
168 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
992 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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257 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
778 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
541 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
206 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
168 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 ...