How to count up an error in svm

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Josef 2013-10-23

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评论： Ilya 2013-10-28

Hello, I'm using 'svmtrain' in MATLAB R2013a and I'm looking for function counting a training error.

I drew a picture where data are separated by the classifier, but there is one red dot in wrong side and that's the error I mean...

So how can i count it up??

Thanks

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Ilya 2013-10-24

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Classification error by definition is the fraction of misclassified observations. So if you have one misclassified point, divide 1 by the number of observations in your data.

Take a look at 'help confusionmat' or 'doc confusionmat'.

Yes, I was trying that, but there is a problem... It works good, but only in linear svm... Another kernels are using own kernel transform of the sv to other dimensions, but I have not found the kernel functions...(or I found them a lot, but which one can I use) :/

Ilya 2013-10-28

I have never seen anyone trying to estimate the geometric margin for non-linear SVM. The geometric margin is only used in textbooks for pedagogical reasons, using the picture just like the one you've attached.

The margin defined as y*f for class label y in set {-1,+1} and soft score f is a useful concept in the learning theory. But that's not what you want.

I suspect you are somewhat confused about what you really want to compute. Either that or I have no idea what you are doing.

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