View Single Post
Old 02-27-2013, 09:06 PM
yaser's Avatar
yaser yaser is offline
Join Date: Aug 2009
Location: Pasadena, California, USA
Posts: 1,478
Default Re: SVM classifier One-vs-One and One-Vs-All clarification

Originally Posted by View Post
I don't understand the question correctly here. For one-vs-one should we pick 2 digits (e.g. 1 and 2) and make them +1 and -1 and rest of the data ignore and try the classification and repeat the exercise for 1,2 1,3 1,4 etc. That would be 10C2 combination. Also for one-vs-all should we do the same but instead of ignoring all the data should we make them all -1?

Then how do we classify 4-vs-all etc.? Really appreciate some help here.
One-versus-one: Once class gets +1 and another class gets -1. Only data from these two classes are considered and the rest of the data is ignored. One has to specify both classes.

One-versus-all: One class gets +1 and all other classes get -1. Data from all classes are considered, and one needs only to specify the "one" class, e.g., 5-versus-all in the digits case.

Both methods can be used as building blocks in a bigger system that distinguishes more digits from each other.
Where everyone thinks alike, no one thinks very much
Reply With Quote