Radial Basis Function with "newrb" dimensional problem

I'm trying to use the function "newrb" for generating an output considering a set of initial inputs and the RBF.

My problem is that as input x I have 5 set of 8 elements (8 coordinates in a 8D space), while as output y I would like to obtain just 1 value (the corresponding 9th coordinates). However, the function said that y must have the same dimension of the value used for x.

To better explain myself, if we consider just 1 set, which has 8 coordinates, I want to use the neural network for obtaining just 1 final value, but I am not allowed to do this since "newrb" required an y with the same dimension of x.

How can I solve this issue??