R help - Jul 2006 - Polynomial kernel in SVM in e1071 package

Dear list,

In some places (for example,
http://en.wikipedia.org/wiki/Support_vector_machine) , the polynomail
kernel in SVM is written as (u'*v + 1)^d, while in the document of
svm() in e1071 package, the polynomial kernel is written as
(gamma*u'*v + coef0)^d.  I am a little confused here:

When doing parameter optimization (grid search or so) for polynomial
kernel, does it need to tune four parameters, gamma, coef0, C and
degree, or just two of them, C and degree (and fixing gamma to 1 and
coef0 = 1)?

Thanks,

Wuming

Wuming Gong wrote:
> Dear list,
> 
> In some places (for example,
> http://en.wikipedia.org/wiki/Support_vector_machine) , the polynomail
> kernel in SVM is written as (u'*v + 1)^d, while in the document of
> svm() in e1071 package, the polynomial kernel is written as
> (gamma*u'*v + coef0)^d.  I am a little confused here:
> 
> When doing parameter optimization (grid search or so) for polynomial
> kernel, does it need to tune four parameters, gamma, coef0, C and
> degree, or just two of them, C and degree (and fixing gamma to 1 and
> coef0 = 1)?
All of them, unless you know reasonable values, but that's very improbable.

Uwe Ligges
> 
> Thanks,
> 
> Wuming
> 
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