Tootfinder

cintestinalis: Tadpole larva brain (C. intestinalis)
Entire connectivity matrix for the complete brain of a larva of Ciona intestinalis. Each directed edge represents a synaptic connection from pre-synaptic cell i to post-synaptic cell j (may not be a neuron). Edge weights represent the cumulative depth of presynaptic contacts in µm.
This network has 205 nodes and 2903 edges.
Tags: Biological, Connectome, Weighted

Weighted Nuclear Elastic Net Estimation of (Near-) Low-Rank Drift Matrices in Ornstein-Uhlenbeck Processes
Dmytro Marushkevych, Francisco Pina, Mark Podolskij
https://arxiv.org/abs/2608.12838 https://arxiv.org/pdf/2608.12838 https://arxiv.org/html/2608.12838
arXiv:2608.12838v1 Announce Type: new
Abstract: We study estimation of the drift matrix in a continuously observed high-dimensional Ornstein-Uhlenbeck process when the drift is exactly or approximately low rank. In this setting, exact low rank induces non-stable directions and hence a non-ergodic regime, resulting in a poorly conditioned empirical covariance matrix. To address this difficulty, we introduce a Weighted Nuclear Elastic Net Estimator that combines ridge regularization with a nuclear-norm penalty expressed in the empirical likelihood geometry.
Under a general diagonalizable spectral framework, we establish oracle inequalities relative to arbitrary low-rank comparison matrices. For near low-rank drifts, the approximation error is naturally measured through the singular-value decay of the drift after weighting by the regularized empirical covariance. The stochastic term is controlled by self-normalized martingale arguments under appropriate choice of the tuning parameter.
For a symmetric positive-semidefinite exact low-rank model, we verify the empirical-curvature condition required to translate the weighted bound into a Frobenius-norm bound. With an appropriate choice of tuning parameters, the resulting estimator satisfies, up to a logarithmic factor, the standard rank-$r$ matrix-estimation scaling $r d/T$: specifically, its squared Frobenius error is of order $r d\log(T)/T$ with high probability, under an explicit dimension-horizon condition.
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cintestinalis: Tadpole larva brain (C. intestinalis)
Entire connectivity matrix for the complete brain of a larva of Ciona intestinalis. Each directed edge represents a synaptic connection from pre-synaptic cell i to post-synaptic cell j (may not be a neuron). Edge weights represent the cumulative depth of presynaptic contacts in µm.
This network has 205 nodes and 2903 edges.
Tags: Biological, Connectome, Weighted

advogato: Advogato trust network (2009)
A network of trust relationships among users on Advogato, an online community of open source software developers. Edge direction indicates that node i trusts node j, and edge weight denotes one of four increasing levels of declared trust from i to j: observer (0.4), apprentice (0.6), journeyer (0.8), and master (1.0).
This network has 6541 nodes and 51127 edges.
Tags: Social, Online, Weighted

college_freshmen: Dutch college freshman (1995)
A small network of friendships among freshmen at Dutch College in 1994-1995. Friendship ties were surveyed at 7 different times over the year, and each edge is timestamped. The direction of an edge indicates that person i named person j, and the edge weight represents their level of friendship, ranging from -1 (risk of conflict) to 3 (best friend).
This network has 32 nodes and 3062 edges.
Tags: Social, Offline, Weighted, Tim…

at_migrations: Austrian internal migrations (2002-2022)
A network of migrations between municipalities in Austria, from 2002 to 2022. A weighted directed link from source to target indicates a migration flow from these two municipalities. Edges are annotated with migration volume (number of people), nationality, sex, and year.
This network has 2115 nodes and 2908569 edges.
Tags: Social, Economic, Travel, Weighted, Politlcal, Timestamps, Metadata

at_migrations: Austrian internal migrations (2002-2022)
A network of migrations between municipalities in Austria, from 2002 to 2022. A weighted directed link from source to target indicates a migration flow from these two municipalities. Edges are annotated with migration volume (number of people), nationality, sex, and year.
This network has 2115 nodes and 2908569 edges.
Tags: Social, Economic, Travel, Weighted, Politlcal, Timestamps, Metadata

advogato: Advogato trust network (2009)
A network of trust relationships among users on Advogato, an online community of open source software developers. Edge direction indicates that node i trusts node j, and edge weight denotes one of four increasing levels of declared trust from i to j: observer (0.4), apprentice (0.6), journeyer (0.8), and master (1.0).
This network has 6541 nodes and 51127 edges.
Tags: Social, Online, Weighted

college_freshmen: Dutch college freshman (1995)
A small network of friendships among freshmen at Dutch College in 1994-1995. Friendship ties were surveyed at 7 different times over the year, and each edge is timestamped. The direction of an edge indicates that person i named person j, and the edge weight represents their level of friendship, ranging from -1 (risk of conflict) to 3 (best friend).
This network has 32 nodes and 3062 edges.
Tags: Social, Offline, Weighted, Tim…

windsurfers: Windsurfers network (1986)
A network of interpersonal contacts among windsurfers in southern California during the Fall of 1986. The edge weights indicate the perception of social affiliations majored by the tasks in which each individual was asked​ to sort cards with other surfer’s name in the order of closeness.
This network has 43 nodes and 336 edges.
Tags: Social, Offline, Weighted