Hi,
I am looking for 'sparse kernels' : kernels which are *exactly* zero for most of
the elements of the kernel matrix. Assume k(a,b) is a kernel function, then
two ways to build such kernels are :
(a) k'(a,b) = max { k(a,b)-q, 0} for some q>=0
{ k(a,b) if k(a,b)>q
(b) k'(a,b) = {
{ 0 otherwise
for some q>=0 (the second method is not continuous)
Does anyone know if any of these methods yield a valid kernel function for
any k(.,.)? for the RBF kernel function? Is there a sparse kernel function (not
built this way)?
Thanks, Koby
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Koby Crammer [log in to unmask]
http://www.cs.huji.ac.il/~kobics
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