899 research outputs found
SOM-VAE: Interpretable Discrete Representation Learning on Time Series
High-dimensional time series are common in many domains. Since human
cognition is not optimized to work well in high-dimensional spaces, these areas
could benefit from interpretable low-dimensional representations. However, most
representation learning algorithms for time series data are difficult to
interpret. This is due to non-intuitive mappings from data features to salient
properties of the representation and non-smoothness over time. To address this
problem, we propose a new representation learning framework building on ideas
from interpretable discrete dimensionality reduction and deep generative
modeling. This framework allows us to learn discrete representations of time
series, which give rise to smooth and interpretable embeddings with superior
clustering performance. We introduce a new way to overcome the
non-differentiability in discrete representation learning and present a
gradient-based version of the traditional self-organizing map algorithm that is
more performant than the original. Furthermore, to allow for a probabilistic
interpretation of our method, we integrate a Markov model in the representation
space. This model uncovers the temporal transition structure, improves
clustering performance even further and provides additional explanatory
insights as well as a natural representation of uncertainty. We evaluate our
model in terms of clustering performance and interpretability on static
(Fashion-)MNIST data, a time series of linearly interpolated (Fashion-)MNIST
images, a chaotic Lorenz attractor system with two macro states, as well as on
a challenging real world medical time series application on the eICU data set.
Our learned representations compare favorably with competitor methods and
facilitate downstream tasks on the real world data.Comment: Accepted for publication at the Seventh International Conference on
Learning Representations (ICLR 2019
Modeling Financial Time Series with Artificial Neural Networks
Financial time series convey the decisions and actions of a population of human actors over time. Econometric and regressive models have been developed in the past decades for analyzing these time series. More recently, biologically inspired artificial neural network models have been shown to overcome some of the main challenges of traditional techniques by better exploiting the non-linear, non-stationary, and oscillatory nature of noisy, chaotic human interactions. This review paper explores the options, benefits, and weaknesses of the various forms of artificial neural networks as compared with regression techniques in the field of financial time series analysis.CELEST, a National Science Foundation Science of Learning Center (SBE-0354378); SyNAPSE program of the Defense Advanced Research Project Agency (HR001109-03-0001
Neural Networks for Complex Data
Artificial neural networks are simple and efficient machine learning tools.
Defined originally in the traditional setting of simple vector data, neural
network models have evolved to address more and more difficulties of complex
real world problems, ranging from time evolving data to sophisticated data
structures such as graphs and functions. This paper summarizes advances on
those themes from the last decade, with a focus on results obtained by members
of the SAMM team of Universit\'e Paris
Analysis of Data Clusters Obtained by Self-Organizing Methods
The self-organizing methods were used for the investigation of financial
market. As an example we consider data time-series of Dow Jones index for the
years 2002-2003 (R. Mantegna, cond-mat/9802256). In order to reveal new
structures in stock market behavior of the companies drawing up Dow Jones index
we apply SOM (Self-Organizing Maps) and GMDH (Group Method of Data Handling)
algorithms. Using SOM techniques we obtain SOM-maps that establish a new
relationship in market structure. Analysis of the obtained clusters was made by
GMDH.Comment: 10 pages, 4 figure
Learning the Pseudoinverse Solution to Network Weights
The last decade has seen the parallel emergence in computational neuroscience
and machine learning of neural network structures which spread the input signal
randomly to a higher dimensional space; perform a nonlinear activation; and
then solve for a regression or classification output by means of a mathematical
pseudoinverse operation. In the field of neuromorphic engineering, these
methods are increasingly popular for synthesizing biologically plausible neural
networks, but the "learning method" - computation of the pseudoinverse by
singular value decomposition - is problematic both for biological plausibility
and because it is not an online or an adaptive method. We present an online or
incremental method of computing the pseudoinverse, which we argue is
biologically plausible as a learning method, and which can be made adaptable
for non-stationary data streams. The method is significantly more
memory-efficient than the conventional computation of pseudoinverses by
singular value decomposition.Comment: 13 pages, 3 figures; in submission to Neural Network
Forecasting of financial data: a novel fuzzy logic neural network based on error-correction concept and statistics
First, this paper investigates the effect of good and bad news on volatility in the BUX return time series using asymmetric ARCH models. Then, the accuracy of forecasting models based on statistical (stochastic), machine learning methods, and soft/granular RBF network is investigated. To forecast the high-frequency financial data, we apply statistical ARMA and asymmetric GARCH-class models. A novel RBF network architecture is proposed based on incorporation of an error-correction mechanism, which improves forecasting ability of feed-forward neural networks. These proposed modelling approaches and SVM models are applied to predict the high-frequency time series of the BUX stock index. We found that it is possible to enhance forecast accuracy and achieve significant risk reduction in managerial decision making by applying intelligent forecasting models based on latest information technologies. On the other hand, we showed that statistical GARCH-class models can identify the presence of leverage effects, and react to the good and bad news.Web of Science421049
Time Series Forecasting: Obtaining Long Term Trends with Self-Organizing Maps
à la suite de la conférence ANNPR, Florence 2003International audienceKohonen self-organisation maps are a well know classification tool, commonly used in a wide variety of problems, but with limited applications in time series forecasting context. In this paper, we propose a forecasting method specifically designed for multi-dimensional long-term trends prediction, with a double application of the Kohonen algorithm. Practical applications of the method are also presented
SOME REMARKS ON THE SELF-ORGANIZING FEATURE MAPS
Joint Research on Environmental Science and Technology for the Eart
Integrated characterisation of mud-rich overburden sediment sequences using limited log and seismic data: Application to seal risk
Muds and mudstones are the most abundant sediments in sedimentary basins and can
control fluid migration and pressure. In petroleum systems, they can also act as source,
reservoir or seal rocks. More recently, the sealing properties of mudstones have been
used for nuclear waste storage and geological CO2 sequestration. Despite the growing
importance of mudstones, their geological modelling is poorly understood and clear
quantitative studies are needed to address 3D lithology and flow properties distribution
within these sediments. The key issues in this respect are the high degree of
heterogeneity in mudstones and the alteration of lithology and flow properties with time
and depth. In addition, there are often very limited field data (log and seismic), with
lower quality within these sediments, which makes the common geostatistical modelling
practices ineffective.
In this study we assess/capture quantitatively the flow-important characteristics of
heterogeneous mud-rich sequences based on limited conventional log and post-stack
seismic data in a deep offshore West African case study. Additionally, we develop a
practical technique of log-seismic integration at the cross-well scale to translate 3D
seismic attributes into lithology probabilities. The final products are probabilistic
multiattribute transforms at different resolutions which allow prediction of lithologies
away from wells while keeping the important sub-seismic stratigraphic and structural
flow features. As a key result, we introduced a seismically-driven risk attribute (so-called
Seal Risk Factor "SRF") which showed robust correspondence to the lithologies
within the seismic volume. High seismic SRFs were often a good approximation for
volumes containing a higher percentage of coarser-grained and distorted sediments, and
vice versa.
We believe that this is the first attempt at quantitative, integrated characterisation of
mud-rich overburden sediment sequences using log and seismic data. Its application on
modern seismic surveys can save days of processing/mapping time and can reduce
exploration risk by basing decisions on seal texture and lithology probabilities
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