Question

Which of the following is not a kernel function?

Answer 1

Solution is as below

Answer 2

Answer:

According to the question option B is the correct answer. K(Xi , Xj ) = ( 1 - Xi.Xj )³ is not a kernel function.

Explanation:

Kernel function is defined as a function that corresponds to a dot product of two feature vectors in some expanded feature spaces:

                 K ( Xa, Xb ) =  Ф(Xa). Ф(Xb)

Often K ( Xa, Xb ) may be very inexpensive to compute even if Ф(Xa) may be extremely high dimensional.

kernel example:

2 dimensional vectors = [ x₁, x₂]