Re: [R] question about SVM in e1071

2010-08-05 Thread Pau Carrio Gaspar
Jack, sorry for the late answer. I agree that my last post is misleading. Here a new try: * * Increasing the value of *C* (...) forces the creation of a more accurate model, that may not generalise well.(Try to imagine the feature space with the two mapped sets very far from each other ) A model t

Re: [R] question about SVM in e1071

2010-07-28 Thread Jack Luo
Pau, Sorry for getting back to you for this again. I am getting confused about your interpretation of 3). It is obvious from your code that increasing C results in* smaller *number of SVs, this seems to contradict with your interpretation " * Increasing the value of C (...) forces the creation of

Re: [R] question about SVM in e1071

2010-07-15 Thread Pau Carrio Gaspar
Hi Jack, to 1) and 2) there are telling you the same. I recommend you to read the first sections of the article it is very well writen and clear. There you will read about duality. to 3) I interpret the scatter plot so: * Increasing the value of C (...) forces the creation of a more accurate mode

Re: [R] question about SVM in e1071

2010-07-14 Thread Jack Luo
Pau, Thanks a lot for your email, I found it very helpful. Please see below for my reply, thanks. -Jack On Wed, Jul 14, 2010 at 10:36 AM, Pau Carrio Gaspar wrote: > Hello Jack, > > 1 ) why do you thought that " larger C is prone to overfitting than smaller > C" ? > *There is some statement

Re: [R] question about SVM in e1071

2010-07-14 Thread Pau Carrio Gaspar
Hello Jack, 1 ) why do you thought that " larger C is prone to overfitting than smaller C" ? 2 ) if you look at the formulation of the quadratic program problem you will see that C rules the error of the "cutting plane " ( and overfitting ). Therfore for hight C you allow that the "cutting plan

[R] question about SVM in e1071

2010-07-13 Thread Jack Luo
Hi, I have a question about the parameter C (cost) in svm function in e1071. I thought larger C is prone to overfitting than smaller C, and hence leads to more support vectors. However, using the Wisconsin breast cancer example on the link: http://planatscher.net/svmtut/svmtut.html I found that th