Bayesian Poisson Tensor Factorization for Inferring ...as5530/ScheinPaisleyBleiWallach2015...Modern...
Transcript of Bayesian Poisson Tensor Factorization for Inferring ...as5530/ScheinPaisleyBleiWallach2015...Modern...
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Bayesian Poisson Tensor Factorization for Inferring Multilateral Relations from Sparse Dyadic Event Counts
John Paisley David M. Blei Hanna WallachAaron ScheinUMass Amherst Columbia University Columbia University Microsoft Research
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E[✓] = a/b
G[✓] = exp( (a))/b
Mode(✓) = (a � 1)/b
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G[✓] = exp( (a))/b
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Dyadic event data
Picture © Kalev Leetaru, available on the GDELT blog
Poisson tensor factorization
Bayesian PTF
Y
Fitting this model is a form of nonnegative CP-Decomposition / PARAFAC:
• Add Gamma priors over factors• Sparsity-inducing with • Posterior inference not point estimation
↵ < 1
Variational inference
Q(⇥(1),⇥(2),⇥(3),⇥(4))
=Y
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Q(✓(1)ik )Y
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Q(✓(2)jk )Y
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Q(✓(3)ak )Y
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Q(✓(4)tk )
Optimize variational parameters to minimize the KL-divergence of the exact posterior from Q!
Point estimates under the Q-distribution:
arithmetic expectation
geometric expectation
Predictive results
Exploratory resultsMotivation• International relations: the field of political
science that studies how countries interact• Modeling goal: Infer multilateral relations
from dyadic event data
Extracted from newspapers:
Modern datasets are bigger, e.g., GDELT:
Sparse event counts
Multilateral relationA coherent thread of international events.
1. sender countries2. receiver countries3. action types4. time steps
Characterized by:
From Schrodt (1993) Event Data in Foreign Policy Analysis:
We compare Bayesian PTF to PTF and NTF-LS (NTF with Euclidean distance). Models are either fit to a dense region of the tensor and tested on a sparse region or vice-versa.
When models are fit to a sparse data, B-PTF generalizes much better.
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European debt crisis: “Europe” is the EU. Germany and Greece are top actors and all diplomatic actions (e.g., Aid) are represented.
1999 East Timorese Crisis: Violence erupts after East Timorese independence claim from Indonesia. Parts of Timor were controlled by Portugal (former colonies). Australia and US served as mediators.
2011 Libyan intervention: NATO, US, France, Italy, UK bomb targets in Libya to stop attacks on civilians by the Qaddafi regime. US-led War in Afghanistan: Peaks immediately following 9/11 (and
invasion). Senders, receivers and action types corroborate. Notice the “blip” in 1998 when Clinton bombed al-Qaeda maps in Afghanistan.
Julian Assange seeks asylum: Wikileaks founder, an Australian national, who was sought by the US and Sweden for separate crimes, requests asylum from Ecuador at their embassy in the UK. The “Stans”: Central Asian relations