How to do multi class classification using Support

Question

In every book and example always they show only binary classification (two classes) and new vector can belong to any one class.

Here the problem is I have 4 classes(c1, c2, c3, c4). I've training data for 4 classes.

For new vector the output should be like

C1 80% (the winner)

c2 10%

c3 6%

c4 4%

How to do this? I'm planning to use libsvm (because it most popular). I don't know much about it. If any of you guys used it previously please tell me specific commands I'm supposed to use.

Answer 1

Commonly used methods are One vs. Rest and One vs. One. In the first method you get n classifiers and the resulting class will have the highest score. In the second method the resulting class is obtained by majority votes of all classifiers.

AFAIR, libsvm supports both strategies of multiclass classification.