Semi-supervised learning of hierarchical latent trait models for data visualisation

Sun, Yi, Tino, Peter, Kaban, Ata and Nabney, Ian T. (2002). Semi-supervised learning of hierarchical latent trait models for data visualisation. Technical Report. Aston University, Birmingham, UK.

Abstract

An interactive hierarchical Generative Topographic Mapping (HGTM) ¸iteH<sub>G</sub>TM has been developed to visualise complex data sets. In this paper, we build a more general visualisation system by extending the HGTM visualisation system in 3 directions: bf (1) We generalize HGTM to noise models from the exponential family of distributions. The basic building block is the Latent Trait Model (LTM) developed in ¸iteKaban<sub>p</sub>ami. bf (2) We give the user a choice of initializing the child plots of the current plot in either em interactive, or em automatic mode. In the interactive mode the user interactively selects ``regions of interest'' as in ¸iteH<sub>G</sub>TM, whereas in the automatic mode an unsupervised minimum message length (MML)-driven construction of a mixture of LTMs is employed. bf (3) We derive general formulas for magnification factors in latent trait models. Magnification factors are a useful tool to improve our understanding of the visualisation plots, since they can highlight the boundaries between data clusters. The unsupervised construction is particularly useful when high-level plots are covered with dense clusters of highly overlapping data projections, making it difficult to use the interactive mode. Such a situation often arises when visualizing large data sets. We illustrate our approach on a toy example and apply our system to three more complex real data sets.

Divisions: Engineering & Applied Sciences > Computer Science
Engineering & Applied Sciences > Systems analytics research institute (SARI)
Uncontrolled Keywords: hierarchical Generative Topographic Mapping,interactive mode,automatic mode,magnification factors,latent trait models,unsupervised construction,overlapping data
Published Date: 2002
Authors: Sun, Yi
Tino, Peter
Kaban, Ata
Nabney, Ian T. ( 0000-0003-1513-993X)

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