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I am trying to calculate the following

$K^{-1}DK^{-1} * p$

Where $K$ is symmetric positive definite and $D$ is positive diagonal and $p$ is a vector. The problem is that p is very, very small so its rounded to zero by Matlab so I want to take the log of of the calculations of $p$ so that I can actually calculate the map above. However if I take the log I need to transform it back somehow.

Can this be done? $K^{-1}$ will naturally contain negative entries.

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    Why not considering a suitable scalar multiple of $p$ instead of the logarithm of the components?2011-03-30
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    Yea. That seems to be it. P in my case is a probability so I do negative log transform and then add the min value to exponential transform. At least I get some non-zeros.2011-04-18

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