The standard norm in RBF treats all dimensions on the same scale. IIRC, someone (Pauli) mentioned on the mailing list before that the data should be standardized. I was just reading the same recommendation in Elements of Statistical Learning. A keyword that would handle standardization (zscore or orthonormalization) internally would be convenient for users. I think it would be possible to use the norm keyword to define a distance measure that is not symmetric in the dimension (mahalanobis), but that requires thinking. just a thought. Josef