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27
Bayesian Model Averaging in proportional hazard models: Assessing the risk of a stroke
 Applied Statistics
, 1997
"... Evaluating the risk of stroke is important in reducing the incidence of this devastating disease. Here, we apply Bayesian model averaging to variable selection in Cox proportional hazard models in the context of the Cardiovascular Health Study, a comprehensive investigation into the risk factors for ..."
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Evaluating the risk of stroke is important in reducing the incidence of this devastating disease. Here, we apply Bayesian model averaging to variable selection in Cox proportional hazard models in the context of the Cardiovascular Health Study, a comprehensive investigation into the risk factors for stroke. We introduce a technique based on the leaps and bounds algorithm which e ciently locates and ts the best models in the very large model space and thereby extends all subsets regression to Cox models. For each independent variable considered, the method provides the posterior probability that it belongs in the model. This is more directly interpretable than the corresponding Pvalues, and also more valid in that it takes account of model uncertainty. Pvalues from models preferred by stepwise methods tend to overstate the evidence for the predictive value of a variable. In our data Bayesian model averaging predictively outperforms standard model selection methods for assessing
Nonparametric Selection of Input Variables for Connectionist Learning
, 1996
"... re. However, for a range of explored problems, the relative ordering of mutual information estimates remains correct, despite inaccuracies in individual estimates. Analysis of forward selection explores the amount of data required to select a certain number of relevant input variables. It is shown t ..."
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Cited by 7 (0 self)
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re. However, for a range of explored problems, the relative ordering of mutual information estimates remains correct, despite inaccuracies in individual estimates. Analysis of forward selection explores the amount of data required to select a certain number of relevant input variables. It is shown that in order to select a certain number of relevant input variables, the amount of required data increases roughly exponentially as more relevant input variables are considered. It is also shown that the chances of forward selection ending up in a local minimum are reduced by bootstrapping the data. Finally, the method is compared to two connectionist methods for input variable selection: Sensitivity Based Pruning and Automatic Relevance Determination. It is shown that the new method outperforms these two when the number of independent, candidate input variables is large. However, the method requires the number of relevant input variables to be relatively small. These results are confirmed o
Greedy Basis Pursuit
, 2006
"... We introduce Greedy Basis Pursuit (GBP), a new algorithm for computing signal representations using overcomplete dictionaries. GBP is rooted in computational geometry and exploits an equivalence between minimizing the ℓ 1norm of the representation coefficients and determining the intersection of th ..."
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We introduce Greedy Basis Pursuit (GBP), a new algorithm for computing signal representations using overcomplete dictionaries. GBP is rooted in computational geometry and exploits an equivalence between minimizing the ℓ 1norm of the representation coefficients and determining the intersection of the signal with the convex hull of the dictionary. GBP unifies the different advantages of previous algorithms: like standard approaches to Basis Pursuit, GBP computes representations that have minimum ℓ 1norm; like greedy algorithms such as Matching Pursuit, GBP builds up representations, sequentially selecting atoms. We describe the algorithm, demonstrate its performance, and provide code. Experiments show that GBP can provide a fast alternative to standard linear programming approaches to Basis Pursuit.
2006b) SPLUS and R package for least angle regression
 In Proceedings of the American Statistical Association, Statistical Computing Section [CDROM
"... Least Angle Regression is a promising technique for variable selection applications, offering a nice alternative to stepwise regression. It provides an explanation for the similar behavior of Lasso (L1penalized regression) and forward stagewise regression, and provides a fast implementation of bot ..."
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Cited by 2 (2 self)
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Least Angle Regression is a promising technique for variable selection applications, offering a nice alternative to stepwise regression. It provides an explanation for the similar behavior of Lasso (L1penalized regression) and forward stagewise regression, and provides a fast implementation of both. We describe a project for creating an opensource SPLUS/R package glars for generalized least angle regression, extending the lars package of Efron and Hastie and glmpath of Park and Hastie. We invite outside collaboration, and plan for future versions of the package to provide a framework on which others can build.
Modellus: Automated Modeling of Complex Internet Data Center Applications
, 2009
"... Distributed server applications have become commonplace in today’s Internet and business environments. The data centers hosting these applications—large clusters of networked servers and storage—have in turn become increasingly complex. Some of this is due to complexity of the applications themselve ..."
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Distributed server applications have become commonplace in today’s Internet and business environments. The data centers hosting these applications—large clusters of networked servers and storage—have in turn become increasingly complex. Some of this is due to complexity of the applications themselves, which may have multiple
Assessment of Response Bias in Mild Head Injury: Beyond Malingering Tests
"... The evaluation of response bias and malingering in cases of mild head injury should not rely on a single test. Initial injury severity, typical neuropsychological test performance patterns, preexisting emotional stress or chronic social difficulties, history of previous neurologic or psychiatric dis ..."
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The evaluation of response bias and malingering in cases of mild head injury should not rely on a single test. Initial injury severity, typical neuropsychological test performance patterns, preexisting emotional stress or chronic social difficulties, history of previous neurologic or psychiatric disorder, other system injuries sustained in the accident, preinjury alcohol abuse, and a propensity to attribute benign cognitive and somatic symptoms to a brain injury must be considered along with performances on measures of response bias. Empirically supported tests and indices are reviewed. Use of the likelihood ratio in diagnosis is shown. Bayesian model averaging as a statistical technique to derive optimal prediction models is demonstrated with a clinical data set. Assessment of Response Bias 3 Assessment of Response Bias in Mild Head Injury: Beyond Malingering Tests Paralleling the increased interest in mild traumatic brain injury (TBI) and use of neuropsychological evidence in the courtroom, numerous comprehensive reviews of the assessment of response bias and malingering of neuropsychological impairment have appeared in the literature over the past decade (e.g., Etcoff & Kampfer, 1996; Iverson & Binder, 2000; Millis & Putnam, 1996; Nies & Sweet, 1994; Rogers, Harrell, & Liff, 1993). Taking the next step in integrating the quickly expanding literature, Slick, Sherman, and Iverson (1999) recently presented diagnostic criteria for "malingered neurocognitive dysfunction (MND)" that are relevant in the assessment of mild TBI. These diagnostic criteria represent a significant contribution to the field because they present a systematic and coherent set of diagnostic guidelines based on empirical findings. Slick et al. (1999) define MND as "...the volitional exaggeration of...
Modellus: Automated Modeling of Complex Data Center Applications
"... The rising complexity of distributed server applications in enterprise data centers has made the tasks of modeling and analyzing their behavior increasingly difficult. This paper presents Modellus, a novel system for automated modeling of complex data center applications using statistical methods fr ..."
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The rising complexity of distributed server applications in enterprise data centers has made the tasks of modeling and analyzing their behavior increasingly difficult. This paper presents Modellus, a novel system for automated modeling of complex data center applications using statistical methods from data mining and machine learning. Modellus can automatically derive models to predict the resource usage of an application and the workload it triggers; these models can be composed to capture multiple dependencies between interacting applications. Model accuracy is maintained by fast, distributed testing, automated relearning of models when they change, and methods to bound prediction errors in composite models. We have implemented a prototype of Modellus, deployed it on a data center testbed, and evaluated its efficacy for modeling and analysis of several distributed server applications. Our results show that this featurebased modeling technique is able to make predictions across several data center tiers, and maintain predictive accuracy (typically 95 % or better) in the face of significant shifts in workload composition; we also demonstrate practical applications of the Modellus system to prediction and provisioning of realworld applications. 1
Performance, Measurement
"... With the ubiquity of multicore processors, software must make effective use of multiple cores to obtain good performance on modern hardware. One of the biggest roadblocks to this is load imbalance, or the uneven distribution of work across cores. We propose LIME, a framework for analyzing parallel ..."
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With the ubiquity of multicore processors, software must make effective use of multiple cores to obtain good performance on modern hardware. One of the biggest roadblocks to this is load imbalance, or the uneven distribution of work across cores. We propose LIME, a framework for analyzing parallel programs and reporting the cause of load imbalance in application source code. This framework uses statistical techniques to pinpoint load imbalance problems stemming from both control flow issues (e.g., unequal iteration counts) and interactions between the application and hardware (e.g., unequal cache miss counts). We evaluate LIME on applications from widely used parallel benchmark suites, and show that LIME accurately reports the causes of load imbalance, their nature and origin in the code, and their relative importance.