257 research outputs found
Adaptive confidence intervals for regression functions under shape constraints
Adaptive confidence intervals for regression functions are constructed under
shape constraints of monotonicity and convexity. A natural benchmark is
established for the minimum expected length of confidence intervals at a given
function in terms of an analytic quantity, the local modulus of continuity.
This bound depends not only on the function but also the assumed function
class. These benchmarks show that the constructed confidence intervals have
near minimum expected length for each individual function, while maintaining a
given coverage probability for functions within the class. Such adaptivity is
much stronger than adaptive minimaxity over a collection of large parameter
spaces.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1068 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Two-Sample Covariance Matrix Testing and Support Recovery
This paper proposes a new test for testing the equality of two covariance matrices Σ1 and Σ2 in the high-dimensional setting and investigates its theoretical and numerical properties. The limiting null distribution of the test statistic is derived. The test is shown to enjoy certain optimality and to be especially powerful against sparse alternatives. The simulation results show that the test significantly outperforms the existing methods both in terms of size and power. Analysis of prostate cancer datasets is carried out to demonstrate the application of the testing procedures. When the null hypothesis of equal covariance matrices is rejected, it is often of significant interest to further investigate in which way they differ. Motivated by applications in genomics, we also consider two related problems, recovering the support of Σ1 − Σ2 and testing the equality of the two covariance matrices row by row. New testing procedures are introduced and their properties are studied. Applications to gene selection is also discussed
Plasmons and screening in monolayer and multilayer black phosphorus
Black phosphorus exhibits a high degree of band anisotropy. However, we found
that its in-plane static screening remains relatively isotropic for momenta
relevant to elastic long-range scattering processes. On the other hand, the
collective electronic excitations in the system exhibit a strong anisotropy.
Band non-parabolicity leads to a plasmon frequency which scales as ,
where is the carrier concentration, and . Screening and
charge distribution in the out-of-plane direction are also studied using a
non-linear Thomas-Fermi model
Testing Differential Networks with Applications to Detection of Gene-Gene Interactions
Model organisms and human studies have led to increasing empirical evidence that interactions among genes contribute broadly to genetic variation of complex traits. In the presence of gene-by-gene interactions, the dimensionality of the feature space becomes extremely high relative to the sample size. This imposes a significant methodological challenge in identifying gene-by-gene interactions. In the present paper, through a Gaussian graphical model framework, we translate the problem of identifying gene-by-gene interactions associated with a binary trai
Locally Adaptive Algorithms for Multiple Testing with Network Structure, with Application to Genome-Wide Association Studies
Linkage analysis has provided valuable insights to the GWAS studies,
particularly in revealing that SNPs in linkage disequilibrium (LD) can jointly
influence disease phenotypes. However, the potential of LD network data has
often been overlooked or underutilized in the literature. In this paper, we
propose a locally adaptive structure learning algorithm (LASLA) that provides a
principled and generic framework for incorporating network data or multiple
samples of auxiliary data from related source domains; possibly in different
dimensions/structures and from diverse populations. LASLA employs a -value
weighting approach, utilizing structural insights to assign data-driven weights
to individual test points. Theoretical analysis shows that LASLA can
asymptotically control FDR with independent or weakly dependent primary
statistics, and achieve higher power when the network data is informative.
Efficiency again of LASLA is illustrated through various synthetic experiments
and an application to T2D-associated SNP identification.Comment: 33 pages, 7 figure
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