41,378 research outputs found
Competing with stationary prediction strategies
In this paper we introduce the class of stationary prediction strategies and
construct a prediction algorithm that asymptotically performs as well as the
best continuous stationary strategy. We make mild compactness assumptions but
no stochastic assumptions about the environment. In particular, no assumption
of stationarity is made about the environment, and the stationarity of the
considered strategies only means that they do not depend explicitly on time; we
argue that it is natural to consider only stationary strategies even for highly
non-stationary environments.Comment: 20 page
Modeling Binary Time Series Using Gaussian Processes with Application to Predicting Sleep States
Motivated by the problem of predicting sleep states, we develop a mixed
effects model for binary time series with a stochastic component represented by
a Gaussian process. The fixed component captures the effects of covariates on
the binary-valued response. The Gaussian process captures the residual
variations in the binary response that are not explained by covariates and past
realizations. We develop a frequentist modeling framework that provides
efficient inference and more accurate predictions. Results demonstrate the
advantages of improved prediction rates over existing approaches such as
logistic regression, generalized additive mixed model, models for ordinal data,
gradient boosting, decision tree and random forest. Using our proposed model,
we show that previous sleep state and heart rates are significant predictors
for future sleep states. Simulation studies also show that our proposed method
is promising and robust. To handle computational complexity, we utilize Laplace
approximation, golden section search and successive parabolic interpolation.
With this paper, we also submit an R-package (HIBITS) that implements the
proposed procedure.Comment: Journal of Classification (2018
Competing with Markov prediction strategies
Assuming that the loss function is convex in the prediction, we construct a
prediction strategy universal for the class of Markov prediction strategies,
not necessarily continuous. Allowing randomization, we remove the requirement
of convexity.Comment: 11 page
Generative Adversarial Networks for Financial Trading Strategies Fine-Tuning and Combination
Systematic trading strategies are algorithmic procedures that allocate assets
aiming to optimize a certain performance criterion. To obtain an edge in a
highly competitive environment, the analyst needs to proper fine-tune its
strategy, or discover how to combine weak signals in novel alpha creating
manners. Both aspects, namely fine-tuning and combination, have been
extensively researched using several methods, but emerging techniques such as
Generative Adversarial Networks can have an impact into such aspects.
Therefore, our work proposes the use of Conditional Generative Adversarial
Networks (cGANs) for trading strategies calibration and aggregation. To this
purpose, we provide a full methodology on: (i) the training and selection of a
cGAN for time series data; (ii) how each sample is used for strategies
calibration; and (iii) how all generated samples can be used for ensemble
modelling. To provide evidence that our approach is well grounded, we have
designed an experiment with multiple trading strategies, encompassing 579
assets. We compared cGAN with an ensemble scheme and model validation methods,
both suited for time series. Our results suggest that cGANs are a suitable
alternative for strategies calibration and combination, providing
outperformance when the traditional techniques fail to generate any alpha
An evaluation of intrusive instrumental intelligibility metrics
Instrumental intelligibility metrics are commonly used as an alternative to
listening tests. This paper evaluates 12 monaural intrusive intelligibility
metrics: SII, HEGP, CSII, HASPI, NCM, QSTI, STOI, ESTOI, MIKNN, SIMI, SIIB, and
. In addition, this paper investigates the ability of
intelligibility metrics to generalize to new types of distortions and analyzes
why the top performing metrics have high performance. The intelligibility data
were obtained from 11 listening tests described in the literature. The stimuli
included Dutch, Danish, and English speech that was distorted by additive
noise, reverberation, competing talkers, pre-processing enhancement, and
post-processing enhancement. SIIB and HASPI had the highest performance
achieving a correlation with listening test scores on average of
and , respectively. The high performance of SIIB may, in part, be
the result of SIIBs developers having access to all the intelligibility data
considered in the evaluation. The results show that intelligibility metrics
tend to perform poorly on data sets that were not used during their
development. By modifying the original implementations of SIIB and STOI, the
advantage of reducing statistical dependencies between input features is
demonstrated. Additionally, the paper presents a new version of SIIB called
, which has similar performance to SIIB and HASPI,
but takes less time to compute by two orders of magnitude.Comment: Published in IEEE/ACM Transactions on Audio, Speech, and Language
Processing, 201
Well-temperate phage: optimal bet-hedging against local environmental collapses
Upon infection of their bacterial hosts temperate phages must chose between
lysogenic and lytic developmental strategies. Here we apply the game-theoretic
bet-hedging strategy introduced by Kelly to derive the optimal lysogenic
fraction of the total population of phages as a function of frequency and
intensity of environmental downturns affecting the lytic subpopulation.
"Well-temperate" phage from our title is characterized by the best long-term
population growth rate. We show that it is realized when the lysogenization
frequency is approximately equal to the probability of lytic population
collapse. We further predict the existence of sharp boundaries in system's
environmental, ecological, and biophysical parameters separating the regions
where this temperate strategy is optimal from those dominated by purely
virulent or} dormant (purely lysogenic) strategies. We show that the virulent
strategy works best for phages with large diversity of hosts, and access to
multiple independent environments reachable by diffusion. Conversely,
progressively more temperate or even dormant strategies are favored in the
environments, that are subject to frequent and severe temporal downturns.Comment: 26 pages, 3 figure
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