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Feed-Forward Neural Networks and Topographic Mappings for Exploratory Data Analysis
- Neural Computing and Applications
, 1996
"... A recent novel approach to the visualisation and analysis of datasets, and one which is particularly applicable to those of a high dimension, is discussed in the context of real applications. A feed-forward neural network is utilised to effect a topographic, structure-preserving, dimension-reducing ..."
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Cited by 49 (2 self)
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A recent novel approach to the visualisation and analysis of datasets, and one which is particularly applicable to those of a high dimension, is discussed in the context of real applications. A feed-forward neural network is utilised to effect a topographic, structure-preserving, dimension-reducing transformation of the data, with an additional facility to incorporate different degrees of associated subjective information. The properties of this transformation are illustrated on synthetic and real datasets, including the 1992 UK Research Assessment Exercise for funding in higher education. The method is compared and contrasted to established techniques for feature extraction, and related to topographic mappings, the Sammon projection and the statistical field of multidimensional scaling. 1 INTRODUCTION The visualisation and analysis of high-dimensional data is a difficult problem and one that may be helpfully viewed in the context of feature extraction, which provides a useful commo...
Quantifying Neighbourhood Preservation in Topographic Mappings
, 1996
"... Mappings that preserve neighbourhood relationships are important in many contexts, from neurobiology to multivariate data analysis. It is important to be clear about precisely what is meant by preserving neighbourhoods. At least three issues have to be addressed: how neighbourhoods are defined, how ..."
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Cited by 27 (5 self)
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Mappings that preserve neighbourhood relationships are important in many contexts, from neurobiology to multivariate data analysis. It is important to be clear about precisely what is meant by preserving neighbourhoods. At least three issues have to be addressed: how neighbourhoods are defined, how a perfectly neighbourhood preserving mapping is defined, and how an objective function for measuring discrepancies from perfect neighbourhood preservation is defined. We review several standard methods, and using a simple example mapping problem show that the different assumptionsof each lead to non-trivially different answers. We also introduce a particular measure for topographic distortion, which has the form of a quadratic assignmentproblem. Many previous methods are closely related to this measure, which thus serves to unify disparate approaches. 1 Introduction Problems of mapping occur frequently both in understanding biological processes and in formulating abstract methods of data an...
Multidimensional Scaling Methods For Many-Object Sets: a Review
"... Given a set of dissimilarities data between n objects, multidimensional scaling is the problem of reconstructing a geometrical pattern of these objects, using n points, so that between-points distance corresponds to between-objects dissimilarity. Often, the collection of input data requires ratin ..."
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Cited by 4 (0 self)
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Given a set of dissimilarities data between n objects, multidimensional scaling is the problem of reconstructing a geometrical pattern of these objects, using n points, so that between-points distance corresponds to between-objects dissimilarity. Often, the collection of input data requires rating the dissimilarities between all n(n\Gamma1) 2 possible pairs of stimuli.
Psychological Approaches to Data Visualisation
, 1998
"... The aim of `data visualisation' is to display a body of information in a way which allows accurate and effortless human comprehension and analysis. Accordingly, the development of data visualisation techniques should be constrained by an understanding of both human perception and cognition. Thi ..."
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Cited by 4 (2 self)
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The aim of `data visualisation' is to display a body of information in a way which allows accurate and effortless human comprehension and analysis. Accordingly, the development of data visualisation techniques should be constrained by an understanding of both human perception and cognition. This report develops and examines a psychological framework for the development of data visualisation techniques based on the notion of similarity structure modelling. Through a series of case studies, a range of established approaches to data visualisation is reviewed and evaluated within this framework, and a number of suggestions for the development of new techniques is made.
Methodology Review
- Analysis of Multitrait-Multimethod Matrices.” Applied Psychological Measurement
, 1986
"... CD4+ CD25+ Foxp3+ regulatory T (Treg) cells are essential to the balance between pro-and anti-inflammatory responses.There are two major subsets ofTreg cells, “natural”Treg (nTreg) cells that develop in the thymus, and “induced ” Treg (iTreg) cells that arise in the periphery from CD4+ Foxp3 − conve ..."
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Cited by 4 (0 self)
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CD4+ CD25+ Foxp3+ regulatory T (Treg) cells are essential to the balance between pro-and anti-inflammatory responses.There are two major subsets ofTreg cells, “natural”Treg (nTreg) cells that develop in the thymus, and “induced ” Treg (iTreg) cells that arise in the periphery from CD4+ Foxp3 − conventional T cells and can be generated in vitro. Previous work has established that both subsets are required for immunological tolerance. Addi-tionally, in vitro-derived iTreg cells can reestablish tolerance in situations where Treg cells are decreased or defective. This review will focus on iTreg cells, drawing comparisons to nTreg cells when possible. We discuss the molecular mechanisms of iTreg cell induction, both in vivo and in vitro, review the Foxp3-dependent and-independent transcriptional land-scape of iTreg cells, and examine the proposed suppressive mechanisms utilized by each Treg cell subset. We also compare the T cell receptor repertoire of the Treg cell subsets, discuss inflammatory conditions where iTreg cells are generated or have been used for treatment, and address the issue of iTreg cell stability. Keywords:Treg cells,Treg stability, immunotherapy,Treg function, gene expression profiling,TCR repertoire
The Use of Psychological Similarity Measure for Queries in Image Databases
, 1996
"... With complex multimedia data, we see the emergence of database systems in which the fundamental operation is similarity assessment. Before database issues can be addressed, it is necessary to give a definition of similarity as an operation. In this paper we study several models proposed in the psych ..."
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Cited by 2 (1 self)
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With complex multimedia data, we see the emergence of database systems in which the fundamental operation is similarity assessment. Before database issues can be addressed, it is necessary to give a definition of similarity as an operation. In this paper we study several models proposed in the psychological literature to explain the characteristics of human similarity assessment, and discuss their computational characteristics. In addition, we develop a similarity measure, based on fuzzy logic, that exhibit several features that match experimental findings in humans. The model is dubbed Fuzzy Feature Contrast (FFC) and is an extension to a more general domain of the Feature Contrast model due to Tversky. We show how the FFC model can be used to model similarity assessment from fuzzy judgment of properties, and we address the use of fuzzy measures to deal with dependencies among the properties. Finally, we show how the parameters of the model can be tuned by comparative judgment experim...
Comparison of Methods for Collecting and Modeling Dissimilarity Data: Applications to Complex Sound Stimuli
"... Sorting procedures are frequently adopted as an alternative to dissimilarity ratings to measure the dissimilarity of large sets of stimuli in a comparatively short time. However, systematic empirical research on the consequences of this experiment-design choice is lacking. We carried out a behaviora ..."
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Sorting procedures are frequently adopted as an alternative to dissimilarity ratings to measure the dissimilarity of large sets of stimuli in a comparatively short time. However, systematic empirical research on the consequences of this experiment-design choice is lacking. We carried out a behavioral experiment to assess the extent to which sorting procedures compare to dissimilarity ratings in terms of efficiency, reliability, and accuracy, and the extent to which data from different data-collection methods are redundant and are better fit by different distance models. Participants estimated the dissimilarity of either semantically charged environmental sounds or semantically neutral synthetic sounds. We considered free and hierarchical sorting and derived indications concerning the properties of constrained and truncated hierarchical sorting methods from hierarchical sorting data. Results show that the higher efficiency of sorting methods comes at a considerable cost in terms of data reliability and accuracy. This loss appears to be minimized with truncated hierarchical sorting methods that start from a relatively low number of groups of stimuli. Finally, variations in data-collection method Correspondence concerning this article should be addressed to Bruno L. Giordano, Schulich
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION PSYCHOLOGICAL APPROACHES TO DATA VISUALISATION
, 1998
"... The aim of 'data visualisation ' is to display a body of information in a way which allows accurate and effortless human comprehension and analysis. Accordingly, the development of data visualisation techniques should be con-strained by an understanding of both human perception and cogniti ..."
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The aim of 'data visualisation ' is to display a body of information in a way which allows accurate and effortless human comprehension and analysis. Accordingly, the development of data visualisation techniques should be con-strained by an understanding of both human perception and cognition. This report develops and examines a psychological framework for the development of data visualisation techniques based on the notion of similarity structure modelling. Through a series of case studies, a range of established approaches to data visualisation is reviewed and evaluated within this framework, and a number of suggestions for the development of new techniques is made. APPROVED FOR PUBLIC RELEASE
Abstract
"... In Information Systems research there are a growing number of studies that must necessarily draw upon the contexts, experiences and narratives of practitioners. This calls for research approaches that are qualitative and may also be interpretive. These may include case studies or action research pro ..."
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In Information Systems research there are a growing number of studies that must necessarily draw upon the contexts, experiences and narratives of practitioners. This calls for research approaches that are qualitative and may also be interpretive. These may include case studies or action research projects. For some researchers, particularly those with limited experience of interpretive qualitative research, there may be a lack of confidence when faced with the prospect of collecting and analysing the data from studies of this kind. In this paper we reflect on the lessons learned from using Grounded Theory in an interpretive case study based piece of research. The paper discusses the lessons and provides guidance for the use of