Function to evaluate the matrix of data vector minus the grid points divided by the bandwidth value.
kfunc(ktype = "normal", difmat)A character string giving the type kernel to be used: "normal", "epanechnikov", "biweight", or "triweight". By default, the "normal" kernel is used.
A numeric matrix of sample data (X) minus evaluation points (x0) divided by bandwidth value (bw).
Returns the matrix resulting from evaluating difmat.