question: @ Override public double calculate_K ( int [ ] x_index , double [ ] x_att , int [ ] y_index , double [ ] y_att ) { double prod = a * innerproduct ( x_index , x_att , y_index , y_att ) + b ; double e1 = Math . exp ( prod ) ; double e2 = Math . exp ( - prod ) ; return ( ( e1 - e2 ) / ( e1 + e2 ) ) ; }
target:  Calculates kernel value of vectors x and y