abstract = "In this paper we propose a genetic programming
approach to learning stochastic models with
unsymmetrical noise distributions. Most learning
algorithms try to learn from noisy data by modelling
the maximum likelihood output or least squared error,
assuming that noise effects average out. While this
process works well for data with symmetrical noise
distributions (such as Gaussian observation noise),
many real-life sources of noise are not symmetrically
distributed, thus this approach does not hold. We
suggest improved learning can be obtained by including
noise sources explicitly in the model as a stochastic
element. A stochastic element is a random sub-process
or latent variable of a hidden system that can
propagate nonlinear noise to the observable outputs.
Stochastic elements can skew and distort output
features making regression of analytical models
particularly difficult and error minimising approaches
inhibiting. We introduce a new method to infer the
analytical model of a system by decomposing non-uniform
noise observed at the outputs into uniform stochastic
elements appearing symbolically inside the system.
Results demonstrate the ability to regress exact
analytical models where stochastic elements are
embedded inside nonlinear and polynomial hidden
systems.",
notes = "GECCO-2007 A joint meeting of the sixteenth
international conference on genetic algorithms
(ICGA-2007) and the twelfth annual genetic programming
conference (GP-2007).