How to use libsvm to get probability output

Question

I would like to use -b option in LIBSVM and could not find an example usage in Matlab. When I try to write this:

svmtrain(bow, [1;0;0;0;0;0;0;0], '-b 1');

I get "Wrong number of arguments" error. When I remove '-b 1' from arguments, in the svmpredict I only get 0 or 1 in result. I want the probability result. How can I do that?

Thanks

Answer 1

The svmtrain function you are calling is not libsvm - it's Matlab's statistics toolbox svmtrain.m!

Use which svmtrain to see which file is actually called. Make sure that you used libsvm's make to compile the necessary libsvm mex files and that they are in Matlab's path. In my installation, I renamed libsvm's svmtrain and svmpredict mex files to libsvm_svmtrain and libsvm_svmpredict in order to avoid this ambiguity.