12,462 research outputs found
Parametric Local Metric Learning for Nearest Neighbor Classification
We study the problem of learning local metrics for nearest neighbor
classification. Most previous works on local metric learning learn a number of
local unrelated metrics. While this "independence" approach delivers an
increased flexibility its downside is the considerable risk of overfitting. We
present a new parametric local metric learning method in which we learn a
smooth metric matrix function over the data manifold. Using an approximation
error bound of the metric matrix function we learn local metrics as linear
combinations of basis metrics defined on anchor points over different regions
of the instance space. We constrain the metric matrix function by imposing on
the linear combinations manifold regularization which makes the learned metric
matrix function vary smoothly along the geodesics of the data manifold. Our
metric learning method has excellent performance both in terms of predictive
power and scalability. We experimented with several large-scale classification
problems, tens of thousands of instances, and compared it with several state of
the art metric learning methods, both global and local, as well as to SVM with
automatic kernel selection, all of which it outperforms in a significant
manner
Quantitative results on continuity of the spectral factorization mapping
The spectral factorization mapping puts a positive definite
integrable matrix function having an integrable logarithm of the
determinant in correspondence with an outer analytic matrix function such
that almost everywhere. The main question addressed here is to
what extent is controlled by and .Comment: 22 page
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