prtKernelDc  DC kernel object
 
  kernelObj = prtKernelDc create a prtKernelDc object that implements a
  constant function.  Kernel objects are widely used in several prt
  classifiers, such as prtClassRvm and prtClassSvm.  DC kernels are
  important in both RVM and SVM classifiers, and are usually included
  to account for any DC offset in the target labels. DC kernels
  implement the following function for 1 x N vectors x1 and x2:
 
   k(x1,x2) = 1;