DOC svm kernel functions docs: rbf equation fixed
@@ -443,7 +443,7 @@ The *kernel function* can be any of the following:
* polynomial: :math:`(\gamma \langle x, x'\rangle + r)^d`.
:math:`d` is specified by keyword ``degree``, :math:`r` by ``coef0``.
- * rbf: :math:`\exp(-\gamma |x-x'|^2)`. :math:`\gamma` is
+ * rbf: :math:`\exp(-\gamma \|x-x'\|^2)`. :math:`\gamma` is
specified by keyword ``gamma``, must be greater than 0.
* sigmoid (:math:`\tanh(\gamma \langle x,x'\rangle + r)`),
