rbfGaussianDerivative
Generates the derivative of a Gaussian Radial Basis Function (RBF) kernel with respect to the distance. The Gaussian RBF is defined as exp(-scale^2 * distance^2). Its derivative with respect to the distance d is -scale^2 * exp(-scale^2 * d^2).
Return
A function representing the derivative of the Gaussian RBF with respect to distance.
Parameters
scale
The scale parameter of the Gaussian RBF. A larger scale results in a wider influence of the RBF.