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Am reading about Reproducing Kernel Hilbert Space(RKHS) while reading through Functional Analysis and Hilbert Space material and am unable to get the notation :

$k(·,xi)$ correctly. What does the dot '.' signify? $k$ is a p.s.d kernel and $xi$ is a point in real space. I have a background in linear algebra, statistics and advanced calculus.

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The dot is a place holder for an appropriate variable. You may have seen this before when denoting inner products $ \| \cdot \|$.

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So, is $k(·,xi)$ a vector, with the placeholder taking all the elements in a vector $x$ other than $x_i$? – qlinck Oct 20 '12 at 20:01

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