How to customize SVM kernel parameters in Matlab
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Hi
I want to ask about how to customize SVM kernel parameters in Matlab.
For ex: I have linear kernel, polynomial kernel, and RBF kernel with:
C = 0.2;
gamma = 0.8;
r = 0.05;
d = 3;
My question is how do I customize it using svmstruct.
1. linear: ??
2. polynomial: ??
3. RBF:
svmstruct = svmtrain(data, groups, 'Kernel_Function', 'rbf', 'RBF_Sigma', 0.2, 'BoxConstraint', 0.8);
CMIIW about how to customize RBF kernel.
I'd really appreciate if anybody could help my research. Thanks.
Regards
Ikra
回答（2 个）
Ahmed
2013-6-10
Documentation given by
help svmtrain
should give you all information you need. What is the meaning of your variable r?
1. the linear kernel has only parameter C
svmstruct = svmtrain(data, groups, 'Kernel_Function', 'linear', 'BoxConstraint', 0.2);
2. polynomial has parameters C and polyorder
svmstruct = svmtrain(data, groups, 'Kernel_Function', 'polynomial', 'polyorder',3,'BoxConstraint', 0.2);
3. RBF
you might have mixed up the constants C and gamma in your code
6 个评论
Ikra89
2013-6-10
Ahmed
2013-6-10
It looks like Matlab's svmtrain function only supports homogeneous polynomial kernels. You can however, define an arbitrary kernel function and pass a handle of it to svmtrain. See section kernel_function -> @kfun in the documentation for description and example.
Ikra89
2013-6-12
Ahmed
2013-7-6
Using an anonymous function of a linear kernel would be:
svmstruct = svmtrain(data, groups, ...
'Kernel_Function',@(x1,x2) x1*x2','BoxConstraint', 0.2);
Note, that your kernel function must lead to a valid kernel.
behruz
2015-7-4
hi the combination of C and gamma how is implemented? in fitcsvnm or svmtrain we dont have any gamma factor how is the impact of it apllied to svm?
behruz
2015-7-5
any comment?
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