Visual Clustering and Classification: The Oronsay Particle Size Data Set Revisted

By

Adalbert F. X. Wilhelm

Edward J. Wegman

and

Jürgen Symanzik

ABSTRACT

Interactive statistical graphics can be effectively used to find natural groupings in observations. In this paper we want to demonstrate how clustering and classification can be done with three approaches based on highly interactive graphical environments: high-dimensional scatterplots as available in XGobi, parallel coordinate plots as available in ExplorN, and linked low-dimensional views as available in Manet. We will point out the strengths and the weaknesses of these techniques by comparing their behavior when applied to the Oronsay particle size data set.

Keywords: High Interaction Graphics, Grand Tour, Parallel Coordinate Plots, Linked Views, XGobi, ExplorN, Manet.

JOURNAL AND TECHNICAL REPORT

This Web site comes in two parts:

• the final journal version of our paper including all color graphics, and
  
  
• the full size technical report with additional graphics and sections that are not available in the journal version.

REFERENCES

The Oronsay particle data set has been extensively analyzed in the literature. Main references are:

• Fieller, N. R. J., Flenley, E. C., and Olbricht, W. (1992), Statistics of Particle Size Data, Journal of the Royal Statistical Society, Series C (Applied Statistics) 41(1), 127-146.
  
  
• Fieller, N. R. J., Gilbertson, D. D., and Olbricht, W. (1984), A new Method for Environmental Analysis of Particle Size Distribution Data from Shoreline Sediments, Nature 311, 648-651.
  
  
• Fieller, N. R. J., Gilbertson, D. D., Olbricht, W., and Timmins, D. A. Y. (1983), A Computer-Compatible Archive of Sedimentological Data from Oronsay, Inner Hebrides, Archive No. 2, Department of Prehistory and Archaeology, University of Sheffield, Sheffield, UK.
  
  
• Fieller, N. R. J., Gilbertson, D. D., and Timmins, D. A. Y. (1987), Sedimentological Analyses of the Shell-Midden Sites, in P. A. Mellars, ed., Excavations on Oronsay: Prehistoric Human Ecology on a Small Island, Edinburgh University Press, Edinburgh, UK, pp. 78-90.
  
  
• Flenley, E. C., and Olbricht, W. (1993), Classification of Archaeological Sands by Particle Size Analysis, in O. Opitz, B. Lausen, and R. Klar, eds, Information and Classification. Concepts, Methods and Applications. Proceedings of the 16th Annual Conference of the Gesellschaft für Klassifikation e. V., Springer, Berlin, Heidelberg, pp. 478-489.
  
  
• Olbricht, W. (1982), Modern Statistical Analysis of Ancient Sand, MSc Thesis, University of Sheffield, Sheffield, UK.
  
  
• Timmins, D. A. Y. (1981), Study of Sediment in Mesolithic Middens on Oronsay, MA Thesis, University of Sheffield, Sheffield, UK.

DATA

You can download the Oronsay data files through this site:

• Oronsay.raw_data: This is the raw particle size data used for our analysis. This file has been processed for use in XGobi (see the next 4 files below). The data has been updated similarly for use in ExplorN and Manet.
  
  
• Oronsay.dat: This file contains the space delimited particle sizes plus two extra columns for all 226 samples. While some of the references speak of 227 samples, this data set does not contain sample CC3_9. Exactly these 226 samples are used in Flenley and Olbricht (1993).

  The first column contains weights for particle sizes >2.0mm, the second column weights for particle sizes 1.4-2.0mm, and so on. Column 13 is the total weight for this sample and column 14 is the group identifier.
  
  

• Oronsay.col: These are the 14 variable names for the particle size data (including total weight and group identifier).
  
  
• Oronsay.row: These are the individual site codes and identifiers for each of the 226 samples.
  
  
• Oronsay.colors: Within each of the 22 known groups, the first two samples have been brushed as a training set. Yellow represents the archaeological training samples, red the CC beach samples, Orange the CC dune samples, green the CNG beach samples, and blue the CNG due samples.

ACKNOWLEDGMENTS

We would like to thank Nick Fieller for providing us with the Oronsay particle size data set (including the permission to post it on this Web site) and additional background information. Thanks are also due to Walter Olbricht for his additional comments and to Qiang Luo who assisted with the preparation of data and the analysis.