# [NRG] Reminder: NRG Meeting: Targeted Matrix Completion (Natali Ruchansky) @ Mon Dec 9, 2013 11am - 12pm (NRG Calendar)

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Title: NRG Meeting: Targeted Matrix Completion (Natali Ruchansky)
Title: Targeted Matrix Completion

Presenter: Natali Ruchansky

Abstract:
In many problems the input consists of a partially-observed matrix and the
goal is to identify a low-rank matrix that best fits these observations.
This task, known as matrix completion, has in recent years become
recognized as fundamental in data analysis.   Traditional statistical
approaches formulate the matrix completion problem as an optimization one,
assuming that the set of observed entries is sufficient for accurate
reconstruction with high probability.  A major drawback is that such
methods give no indication of which entries have been accurately recovered
and which not -- since they output some completion for any set of
observations, even the smallest.
On the other hand, the recent structural completion methods (such as the
Information Cascade Matrix Completion method we adopt) evaluate the
positions of observed entries and indicate precisely which missing entries
can be recovered accurately.  Here, we ask the following natural question:
when the observations are not enough to recover all entries, how can we add
observations to enable full completion?  One strategy is to randomly reveal
entries until a density at which statistical methods can output a good
estimate.  Unfortunately this density can be rather high, and so we wonder
if there is a smarter way.  Through a deep understanding of structural
completion, we introduce an algorithm called Order&Extend that chooses
entries strategically.  Together with structural completion, our algorithm
can identify exactly which entries can be recovered given the observation,
and then specify how much and which additional information is needed for
full completion.  We show that Order&Extend requires less (almost minimal)
information and leads to better recovery than statistical methods.

Short Bio:
Natali received a Bachelor of Art from Boston University in Mathematics and
Computer Science.  She is now a PhD student in the Data Management Lab at
Boston University, working with Evimaria Terzi and Mark Crovella.  Her
research interests span many topics including algorithmic data mining and
mathematics.

When: Mon Dec 9, 2013 11am – 12pm Eastern Time
Where: MCS-148, 111 Cummington Mall, Boston, MA 02215
Calendar: NRG Calendar
Who:
* Larissa Spinelli - creator

Event details:
https://www.google.com/calendar/event?action=VIEW&eid=bHR2bXVvdnBmZDRhdWRzaHRkcXFkdDVmamcgNTYwam42bnQ1aGo0b2YzcnNyaWNoZnB0aW9AZw

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