Monte Carlo for Robust Regression: The Swindle Unmasked

This paper gives an alternative derivation of a Monte Carlo method that has been used to study robust estimators. Extensions of the technique to the regression case are also considered and some computational points are briefly mentioned.

A System of Subroutines For Iteratively Reweighted Least Squares Computations

A description of a system of subroutines to compute solutions to the iteratively reweighted least squares problem is presented. The weights are determined from the data and linear fit and are computed as functions of the scaled residuals. Iteratively reweighted least squares is a part of robust statistics where "robustness" means relative insensitivity to moderate departures from assumptions. The software for iteratively reweighted least squares is cast as semi-portable Fortran code whose performance is unaffected (in the sense that performance will not be degraded) by the computer or operating-system environment in which it is used. An [ell sub1] start and an [ell sub2] start are provided. Eight weight functions, a numerical rank determination, convergence criterion, and a stem-and-leaf display are included.

Influence of tides on melting and freezing beneath Filchner-Ronne Ice Shelf, Antarctica

An isopycnic coordinate ocean circulation model is applied to the ocean cavity beneath Filchner-Ronne Ice Shelf, investigating the role of tides on sub-ice shelf circulation and ice shelf basal mass balance. Including tidal forcing causes a significant intensification in the sub-ice shelf circulation, with an increase in melting (3-fold) and refreezing (6-fold); the net melt rate and seawater flux through the cavity approximately doubles. With tidal forcing, the spatial pattern and magnitude of basal melting and freezing generally match observations. The 0.22 m a(-1) net melt rate is close to satellite-derived estimates and at the lower end of oceanographic values. The Ice Shelf Water outflow mixes with shelf waters, forming a cold (<-1.9 degrees C), dense overflow (0.83 Sv) that spills down the continental slope. These results demonstrate that tidal forcing is fundamental to both ice shelf-ocean interactions and deep-water formation in the southern Weddell Sea. Citation: Makinson, K., P. R. Holland, A. Jenkins, K. W. Nicholls, and D. M. Holland (2011), Influence of tides on melting and freezing beneath Filchner-Ronne Ice Shelf, Antarctica, Geophys. Res. Lett., 38, L06601, doi: 10.1029/2010GL046462

Statistics and causal inference.

Problems involving causal inference have dogged at the heels of statistics since its earliest days. Correlation does not imply causation, and yet causal conclusions drawn from a carefully designed experiment are often valid. What can a statistical model say about causation? This question is addressed by using a particular model for causal inferenc

Identification of the Regions of the Bovine Genome Associated with Gray Coat Color in a Nellore-Angus Cross Population

The genetics of coat color for cattle are important to breeders and breed associations because phenotypes of these animals are used for breed recognition and premiums or discounts can be given due to the phenotypes. The gene for gray coat color has been determined in other species, but not in cattle. Gray in cattle is known to be recessive based upon observed inheritance. The objective of this study was to identify the regions of the bovine genome associated with gray coat color in a population of Nellore-Angus crossbred cattle. Additionally, proportions of each color and spotting were of interest. Animals (n = 1941) were classified into phenotypic color categories (i.e. red, black, gray, etc.). Proportions of each color group out of the population were determined, and the proportion of those phenotypes that have any form of spotting. Two genome-wide association analyses were conducted, one where phenotypically gray vs. not gray cattle were analyzed and another where cattle that were very light in color but had a reddish tinge were included as gray. Analyses used Bonferroni correction at α = 0.05 (α/ntests = 1.49 × 10^-6). Analysis of gray vs. not gray yielded one significant SNP marker on BTA6 at a location of 68,059,441 bp (Praw = 9.69 × 10^-7, Padjusted = 0.032) (UMD_3.1, NCBI project 32899, Gen Bank GCA_000003055.3). For the analysis of gray and reddish tinged vs. not gray, there were 5 significant markers all on BTA6 forming a region from 62.93 Mb to 83.92 Mb (UMD_3.1, NCBI project 32899, Gen Bank GCA_000003055.3).The same SNP marker from the first analysis was present in the second, but had an increased significance (Praw = 1.50 × 10^-10, Padjusted = 5.02 × 10^-6). The region on BTA6 ruled out syntaxin-17 (STX17) on BTA8 and premelanosome protein (PMEL) on BTA5, previous gray candidate genes from other species, but includes genes such as v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT), which is known to cause white coloration (spotting), and platelet-derived growth factor receptor alpha polypeptide (PDGFRA), the strongest candidate gene for the reddening in Nellore-Angus cattle, and corin serin pepsidase (CORIN), known for lighter coloration

The sensitivity of linear regression coefficients' confidence limits to the omission of a confounder

Omitted variable bias can affect treatment effect estimates obtained from observational data due to the lack of random assignment to treatment groups. Sensitivity analyses adjust these estimates to quantify the impact of potential omitted variables. This paper presents methods of sensitivity analysis to adjust interval estimates of treatment effect---both the point estimate and standard error---obtained using multiple linear regression. Central to our approach is what we term benchmarking, the use of data to establish reference points for speculation about omitted confounders. The method adapts to treatment effects that may differ by subgroup, to scenarios involving omission of multiple variables, and to combinations of covariance adjustment with propensity score stratification. We illustrate it using data from an influential study of health outcomes of patients admitted to critical care.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS315 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

New sub-millimeter limits on dust in the 55 Cancri planetary system

We present new, high-sensitivity sub-millimeter observations towards 55 Cancri, a nearby G8 star with one, or possibly two, known planetary companion(s). Our 850 $\mu$m map, obtained with the SCUBA instrument on the James Clerk Maxwell Telescope, shows three peaks of emission at the 2.5 mJy level in the vicinity of the star's position. However, the observed peaks are 25\arcsec--40\arcsec away from the star and a deep $R$-band optical image reveals faint point sources that coincide with two of the sub-millimeter peaks. Thus, we do not find evidence for dust emission spatially associated with 55 Cancri. The excess 60 $\mu$m emission detected with ISO may originate from one or more of the 850 $\mu$m peaks that we attribute to background sources. Our new results, together with the HST/NICMOS coronographic images in the near-infrared, place stringent limits on the amount of dust in this planetary system, and argue against the existence of a detectable circumstellar dust disk around 55 Cnc.Comment: 11 pages, 2 PostScript figures, to appear in The Astrophysical Journal Letter

Effect of urinary pH and diatrizoate on Bence Jones protein nephrotoxicity in the rat

Effect of urinary pH and diatrizoate on Bence Jones protein nephrotoxicity in the rat. Both low urinary pH and radiocontrast agents may intensify myeloma nephrotoxicity. To study the effects of these factors, we determined inulin clearances (CIn) before and after infusions of human Bence Jones protein (BJP) in male Sprague-Dawley rats in a dose previously shown to be nephrotoxic. Rats that drank 0.15 M NaHCO3 for 48 hr before study had no change in CIn (+ 3 ± 20%) after BJP unlike those that drank 0.15 M NH4Cl (- 33 ± 14%, P < 0.05); urinary pH differed (7.6 ± 0.1 vs. 6.2 ± 0.1, P < 0.05), but urinary flow rates did not. The acidifying regimen was used in all subsequent groups. Infusion of diatrizoate (DTZ) after BJP produced a further decrease in CIn (- 85 ± 8%, P < 0.05). In contrast, infusion of albumin, which raised plasma protein concentration to that seen in BJP-infused rats, did not change CIn (+ 39 ± 17%). Infusion of beta-lactoglobulin also led to a greater decrease in CIn after DTZ (- 35 ± 9 vs. - 67 ± 8%, P < 0.05), but myoglobin did not (- 58 ± 7 vs. - 54 ± 12%). Urinary pH and flow rate did not differ between any DTZ-infused group and its appropriate control. These data suggest that aciduria independent of urinary flow rate increases the nephrotoxicity of BJP. In this setting, DTZ further intensifies the nephrotoxicity of BJP as well as some but not all filterable proteins.Effet du pH urinaire et du diatrizoate sur la néphrotoxicité de la protéine de Bence Jones chez le rat. Un pH urinaire bas et les produits de contraste peuvent accroître la néphrotoxité du myélome. Pour étudier les effets de ces facteurs, nous avons déterminé les clearances de l'inuline (CIn) avant et après perfusion de protéine de Bence Jones humaine (BJP) chez des rats mâles Sprague-Dawley à dose préalablement montrée néphrotoxique. Les rats qui buvaient 0,15 M NaHCO3 pendant 48 hr avant l'étude n'avaient pas de modification de CIn (+ 3 ± 20%) après BJP à la différence de ceux qui buvaient 0,15 M NH4Cl (- 33 ± 14%, P < 0,05); les pH urinaires différaient (7,6 ± 0,1 contre 6,2 ± 0,1, P < 0,05), mais non les débits urinaires. Le régime acidifiant a été utilisé chez tous les groupes ultérieurs. La perfusion de diatrizoate (DTZ) après BJP a entraîné une diminution supplémentaire de CIn (- 85 ± 8%, P < 0,05). A l'opposé une perfusion d'albumine, qui augmentait la protidémie à la valeur observée chez les rats perfusés avec BJP ne modifiait pas CIn (+ 39 ± 17%). Une perfusion de béta-lactoglobuline a également entraîné une plus forte baisse de CIn après DTZ (- 35 ± 9 contre - 67 ± 8%, P < 0,05), mais non de la myoglobine (- 58 ± 7 contre - 54 ± 12%). Le pH et le débit urinaires ne différaient pas entre aucun des groupes perfusés par le DTZ et leur contrôle approprié. Ces données suggèrent que l'acidurie, indépendamment du débit urinaire, augmente la néphrotoxicité de la BJP. Dans ce schéma, DTZ accentue encore la néphrotoxicité de la BJP, de même que certaines, mais non toutes les protéines filtrables

Simultaneous Estimation of Multinomial Cell Probabilities

1 online resource (PDF, 34 pages

EdMot: An Edge Enhancement Approach for Motif-aware Community Detection

Network community detection is a hot research topic in network analysis. Although many methods have been proposed for community detection, most of them only take into consideration the lower-order structure of the network at the level of individual nodes and edges. Thus, they fail to capture the higher-order characteristics at the level of small dense subgraph patterns, e.g., motifs. Recently, some higher-order methods have been developed but they typically focus on the motif-based hypergraph which is assumed to be a connected graph. However, such assumption cannot be ensured in some real-world networks. In particular, the hypergraph may become fragmented. That is, it may consist of a large number of connected components and isolated nodes, despite the fact that the original network is a connected graph. Therefore, the existing higher-order methods would suffer seriously from the above fragmentation issue, since in these approaches, nodes without connection in hypergraph can't be grouped together even if they belong to the same community. To address the above fragmentation issue, we propose an Edge enhancement approach for Motif-aware community detection (EdMot). The main idea is as follows. Firstly, a motif-based hypergraph is constructed and the top K largest connected components in the hypergraph are partitioned into modules. Afterwards, the connectivity structure within each module is strengthened by constructing an edge set to derive a clique from each module. Based on the new edge set, the original connectivity structure of the input network is enhanced to generate a rewired network, whereby the motif-based higher-order structure is leveraged and the hypergraph fragmentation issue is well addressed. Finally, the rewired network is partitioned to obtain the higher-order community structure.Comment: 9 pages, 4 figures, Accepted by KDD 1