416 research outputs found
Ensemble of Example-Dependent Cost-Sensitive Decision Trees
Several real-world classification problems are example-dependent
cost-sensitive in nature, where the costs due to misclassification vary between
examples and not only within classes. However, standard classification methods
do not take these costs into account, and assume a constant cost of
misclassification errors. In previous works, some methods that take into
account the financial costs into the training of different algorithms have been
proposed, with the example-dependent cost-sensitive decision tree algorithm
being the one that gives the highest savings. In this paper we propose a new
framework of ensembles of example-dependent cost-sensitive decision-trees. The
framework consists in creating different example-dependent cost-sensitive
decision trees on random subsamples of the training set, and then combining
them using three different combination approaches. Moreover, we propose two new
cost-sensitive combination approaches; cost-sensitive weighted voting and
cost-sensitive stacking, the latter being based on the cost-sensitive logistic
regression method. Finally, using five different databases, from four
real-world applications: credit card fraud detection, churn modeling, credit
scoring and direct marketing, we evaluate the proposed method against
state-of-the-art example-dependent cost-sensitive techniques, namely,
cost-proportionate sampling, Bayes minimum risk and cost-sensitive decision
trees. The results show that the proposed algorithms have better results for
all databases, in the sense of higher savings.Comment: 13 pages, 6 figures, Submitted for possible publicatio
COMET: A Recipe for Learning and Using Large Ensembles on Massive Data
COMET is a single-pass MapReduce algorithm for learning on large-scale data.
It builds multiple random forest ensembles on distributed blocks of data and
merges them into a mega-ensemble. This approach is appropriate when learning
from massive-scale data that is too large to fit on a single machine. To get
the best accuracy, IVoting should be used instead of bagging to generate the
training subset for each decision tree in the random forest. Experiments with
two large datasets (5GB and 50GB compressed) show that COMET compares favorably
(in both accuracy and training time) to learning on a subsample of data using a
serial algorithm. Finally, we propose a new Gaussian approach for lazy ensemble
evaluation which dynamically decides how many ensemble members to evaluate per
data point; this can reduce evaluation cost by 100X or more
Gossip Learning with Linear Models on Fully Distributed Data
Machine learning over fully distributed data poses an important problem in
peer-to-peer (P2P) applications. In this model we have one data record at each
network node, but without the possibility to move raw data due to privacy
considerations. For example, user profiles, ratings, history, or sensor
readings can represent this case. This problem is difficult, because there is
no possibility to learn local models, the system model offers almost no
guarantees for reliability, yet the communication cost needs to be kept low.
Here we propose gossip learning, a generic approach that is based on multiple
models taking random walks over the network in parallel, while applying an
online learning algorithm to improve themselves, and getting combined via
ensemble learning methods. We present an instantiation of this approach for the
case of classification with linear models. Our main contribution is an ensemble
learning method which---through the continuous combination of the models in the
network---implements a virtual weighted voting mechanism over an exponential
number of models at practically no extra cost as compared to independent random
walks. We prove the convergence of the method theoretically, and perform
extensive experiments on benchmark datasets. Our experimental analysis
demonstrates the performance and robustness of the proposed approach.Comment: The paper was published in the journal Concurrency and Computation:
Practice and Experience
http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291532-0634 (DOI:
http://dx.doi.org/10.1002/cpe.2858). The modifications are based on the
suggestions from the reviewer
Measuring confidence of missing data estimation for HIV classification
Computational intelligence methods have been applied to classify pregnant women’s HIV status
using demographic data from the South African Antenatal Seroprevalence database obtained
from the South African Department of Health. Classification accuracies using a multitude of
computational intelligence techniques ranged between 60% and 70%. The purpose of this
research is to determine the certainty of predicting the HIV status of a patient. Ensemble
neural networks were used for the investigation to obtain a set of possible solutions. The
predictive certainty of each patients predicted HIV status was computed by giving the
percentage of most dominant outputs from the set of possible solutions. Ensembles of neural
networks were obtained using boosting, bagging and the Bayesian approach. It was found that
the ensemble trained using the Bayesian approach is most suitable for the proposed predictive
certainty measure. Furthermore, a sensitivity analysis was done to investigate how each of the
demographic variables influenced the certainty of predicting the HIV status of a patien
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