All Questions
Tagged with kernel-trick libsvm
21 questions
2
votes
2
answers
7k
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(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 ...
1
vote
0
answers
148
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Solving SVM with multiple linear kernels
I am trying to implement a variant of SVM in C++ that takes in a gram matrix G and a target vector Y. Here is the formulation of the problem:
$$min \frac{1}{2}\alpha^TY(\sum_{t=1}^{T}u_tX_t{X_t}^T)Y\...
- 213
2
votes
1
answer
284
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Is $b$ in Support Vector Regression constant or not?
In Support Vector Regression, the following dual optimization problem is solved with respect to $\alpha_i$ and $\alpha_i^*$:
\begin{equation}
\begin{aligned}
& \text{maximize} && \begin{...
- 2,440
1
vote
0
answers
383
views
how to get feature map for a given kernel function
With respect to support vector machine, there are multiple types of kernels, such as The Gaussian Kernel, The homogeneous kernel,...
- 5,282
1
vote
0
answers
311
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Can you give me a short step by step numerical example of radial basis function kernel trick? I would like to understand how to apply on perceptron
I understand well perceptron so put accent only on kernel but I am not familiar with matemathic expressions so please give me an numerical example and a guide on kernel.
For example:
My hyperplane ...
2
votes
1
answer
329
views
What will be the input value (i.e. $x$ and $x′$) of RBF kernel for a given dataset or data matrix $x$?
If $x$ is a data matrix or dataset then What will be the input value (i.e. $x$ and $x'$) of RBF kernel $K_r(x,x')=\exp(-\frac{\|x-x'\|^2}{r})$ ?
I can understand $x$ is same as dataset or data matrix ...
- 173
0
votes
1
answer
615
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How to justify the usage of "Radial Basis Function" as a kernel for SVM [duplicate]
I ran SVM with several kernels on my data. RBS has the best performing results. The task is similar to the text classification. I wonder how I can explain why RBS is actually the best kernel for my ...
- 275
0
votes
1
answer
376
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What does the number 'Kernel Option' refer to in SVM?
I read that the performance of some kernel functions in SVM can change if we change the number known as kernel option. For example, this article states that kernel option of value 2 was used, http://...
- 101
4
votes
1
answer
94
views
Machine Learning SVM
If one trains a model using a SVM from kernel data, the resultant trained model contains support vectors. Now consider the case of training a new model using the old data already present plus a small ...
- 51
4
votes
1
answer
278
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linear kernel SVM
The linear kernel is defined as: $K(x1,x2)=\langle x1,x2\rangle$. I can see that all that this kernel does is to calculate the dot product in the original space of the data. Why is this kernel then ...
- 1,421
5
votes
1
answer
2k
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How to prove that text is linearly separable?
I sentiment analisys task, for this I used SVM with an rbf kernel and a linear one. The results for the linear kernel were better than the rbf, from this I know that text is linearly separable, but ...
- 231
2
votes
0
answers
353
views
Support Vector Machine with zero bias term
I'm looking for an algorithm to solve SVM with zero bias term. So dual form of such SVM is $max_\alpha \sum_i^n \alpha_i -1/2\sum_i^n \sum_j^ny_iy_jK(x_ix_j)\alpha_i\alpha_j$
subject to: $0 \leq \...
- 243
0
votes
1
answer
797
views
What is the toolkit that implements Cost sensitive Support Vector Machine?
I need implementation of cost sensitive support vector machine. The cost is different for each training example (unlike each class). So problem is to solve
$max_\alpha$ $-1/2 \sum_{i,j} \alpha_i\...
- 243
2
votes
1
answer
1k
views
Extracting decision function variable from libsvm
I'm trying to use LIBSVM's single class SVMs for some classification and need to extract the following sum post classification (i.e. the variable that the decision function takes in)
$$
\Sigma_{i=1}^{...
- 65
9
votes
2
answers
14k
views
Plotting the decision boundary of a kernel SVM (RBF)
Suppose we are given a training set of 2D points that are linearly non-separable. I train a binary SVM with an RBF kernel in order to classify them. What I want to do is to draw the desicion boundary.
...
- 353
0
votes
1
answer
86
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Evolution strategies in libsvm
I'm working on a protein multi-classification problem, using libsvm and the edit distance kernel. This kernel depends on a parameter $\gamma$. I'm able to get the best parameters ($\gamma$ and $C$) ...
- 11
0
votes
1
answer
620
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Accuracy changes with permutation of input data in Libsvm with precomputed kernel?
I'm doing quite simple SVM classification at the moment. I use a precomputed kernel in LibSVM with RBF and DTW.
When I compute the similarity (kernel-) matrix, everything seems to work very fine ... ...
- 11
1
vote
1
answer
1k
views
The Lagrange multipliers of SVM
Actually the solve the SVM is to solve the following Lagrangian Equation:
If we don't use kernel function, $\langle x^{(i)},x^{(j)}\rangle$ is just the vector vector inner product. The $a_ia_j\langle ...
- 183
10
votes
2
answers
20k
views
Which SVM kernel to use for a binary classification problem?
I'm a beginner when it comes to support vector machines. Are there some guidelines that say which kernel (e.g. linear, polynomial) is best suited for a specific problem? In my case, I have to classify ...
- 445
9
votes
2
answers
10k
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Use of the Gamma parameter with support vector machines
When using libsvm, the parameter $\gamma$ is a parameter for the kernel function. Its default value is setup as $$\gamma = \frac{1}{\text{number of features.}}$$
...
- 5,282
8
votes
4
answers
4k
views
Support vector machine for text classification
I am currently having a data set, class 1 with about 8000 short text files and class 2 with about 3000 short text files. I applied LibSVM and tried a couple of parameter combinations in the cross-...
- 3,089