dear friend

The Nu value is the optimization parameter.

The value of Nu tell you how much "precision" is involved in your computations.

look, "Precision" is different from "Accuracy%" . Kindly see my papers for more details.

I hope this helps you .

Best regards

Dr. Indrajit Mandal

Dear Aliakbari

According to Tax paper's that its link is attached to this post, Nu is regularization parameter  member of (0,1) interval that shows how much data should be separate like C in SVDD. But remember that in sample space of Nu-SVC we speak in normal vector therefore if we speak in normalized vector C'=1/Nu.N. For more detail refer to bellow paper page 50.

Best Regards

http://link.springer.com/article/10.1023%2FB%3AMACH.0000008084.60811.49