[mlpack-git] [mlpack] DET has only one leaf prior to pruning every time (#515)

[Ryan Curtin]

Diagnosis: the log negative error of a DET is defined as

R(t) = log(|t|^2 / (N^2 V_t)).

At the first level of this tree, the volume of the node is the entire volume spanned by the data.  i.e. V = the width of every dimension multiplied together.  But some dimensions have width 0 in this dataset, so, V = 0 and R(t) = inf.

I don't yet know how I want to handle this problem for the mlpack code; I need to review the paper and maybe send Pari an email or something depending on what I can come up with.

A quick solution is to add tiny bits of noise to your data points, or to drop any dimensions that have zero range (i.e. where all of the rows have 0 in that dimension).

I'll keep digging and let you know what I think of.

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Reply to this email directly or view it on GitHub:
https://github.com/mlpack/mlpack/issues/515#issuecomment-182569695
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