SVM regression with C=0

adrian_loy

Hello everyone,

 

I dont understand why one would want to perform SVM regression with C=0. All papers that i read in that topic talk about C > 0, because otherwise points do not get punished at all if they lie outside the tube, which means the position of the tube does not matter at all and the result should be very bad. Is the default value for C really 0 or is it 0.000001 or something like that? I also realized you can enter C=-1. What is this supposed to mean? And how can I set the value to infinity to get hard boundaries?

 

Thanks in advance for every reply!

 

Greetings,

Adrian

IngoRM

Hi,

 

Thanks for asking - I just realized that the docs are not making a good job explaining this.  Anyway, a value of 0 indicates that we use a heuristic described in this post here to determine a value for C based on the provided data:

 

http://community.rapidminer.com/t5/RapidMiner-Studio/issue-of-setting-up-C-0-when-using-Libsvm-operator-in-Rapidminer/m-p/21226

 

Unfortunately, I still do not remember exactly where we found this :smileytongue:

 

Negative values are indeed not possible (nor do they make sense), not sure why the UI allows -1...

 

Hope this helps,

Ingo