function k = kernel(x, y);% function k = kernel(x, y);%%	x: (Lx,N) with Lx: number of points; N: dimension%	y: (Ly,N) with Ly: number of points%	k: (Lx,Ly)%%	KTYPE = 1:      linear kernel:      x*y'%	KTYPE = 2,3,4:  polynomial kernel:  (x*y'*KSCALE+1)^KTYPE%	KTYPE = 5:      sigmoidal kernel:   tanh(x*y'*KSCALE)%	KTYPE = 6:	gaussian kernel with variance 1/(2*KSCALE)%%       assumes that x and y are in the range [-1:+1]/KSCALE (for KTYPE<6)global KTYPEglobal KSCALEk = x*y';if KTYPE == 1				% linear    % take as iselseif KTYPE <= 4			% polynomial    k = (k*KSCALE+1).^KTYPE;elseif KTYPE == 5			% sigmoidal    k = tanh(k*KSCALE);elseif KTYPE == 6			% gaussian    [Lx,N] = size(x);    [Ly,N] = size(y);    k = 2*k;    k = k-sum(x.^2,2)*ones(1,Ly);    k = k-ones(Lx,1)*sum(y.^2,2)';    k = exp(k*KSCALE);end