COOKIES: By using this website you agree that we can place Google Analytics Cookies on your device for performance monitoring. |

University of Cambridge > Talks.cam > Cambridge Analysts' Knowledge Exchange > Local nearest neighbour classification with applications to semi-supervised learning

## Local nearest neighbour classification with applications to semi-supervised learningAdd to your list(s) Download to your calendar using vCal - Thomas Berrett (University of Cambridge)
- Wednesday 31 May 2017, 16:00-17:00
- MR14, Centre for Mathematical Sciences.
If you have a question about this talk, please contact Nicolai Baldin. In this talk I will present a new asymptotic expansion for the global excess risk of a local k-nearest neighbour classifier, where the choice of k may depend upon the test point. This expansion elucidates conditions under which the dominant contribution to the excess risk comes from the locus of points at which each class label is equally likely to occur. Moreover, I will present results which show that, provided the d-dimensional marginal distribution of the features has a finite ρth moment for some ρ>4 (as well as other regularity conditions), a local choice of k can yield a rate of convergence of the excess risk of O(n^(-4/(d+4))), where n is the sample size, whereas for the standard k-nearest neighbour classifier, our theory would require d≥5 and ρ>4d/(d−4) finite moments to achieve this rate. Motivated by these results, I will introduce a new k-nearest neighbour classifier for semi-supervised learning problems, where the unlabelled data are used to obtain an estimate of the marginal feature density, and fewer neighbours are used for classification when this density estimate is small. This talk is part of the Cambridge Analysts' Knowledge Exchange series. ## This talk is included in these lists:- All CMS events
- CMS Events
- Cambridge Analysts' Knowledge Exchange
- DAMTP info aggregator
- Interested Talks
- MR14, Centre for Mathematical Sciences
- My seminars
- bld31
Note that ex-directory lists are not shown. |
## Other listsThe Archimedeans (CU Mathematical Society) CCC talks for website Cambridge Coding Academy free tech talks Collaboration Skills Initiative Group Theory, Geometry and Representation Theory: Abel Prize 2008 Cambridge Lovelace Hackathons## Other talksA domain-decomposition-based model reduction method for convection-diffusion equations with random coefficients Decision Theory for AI safety Loss and damage: Insights from the front lines in Bangladesh New Insights in Immunopsychiatry (Provisional Title) St Johns Linacre Lecture 2018: Professor Sir Peter Ratcliffe FRS |