XGVis(1)XGVis(1)NAMExgvis - interactive multidimensional scaling using xgobi for display
SYNOPSISxgvis [ -dims n ] [ -stepsize x ] fname
DESCRIPTIONxgvis is an interactive multidimensional scaling (MDS) program that
consists of a control panel to manipulate the parameters of the MDS
stress function and an xgobi window for data display. It can be used
either for visualization of dissimilarity data, for dimension reduc‐
tion, or for graph layout. Graph layout is usually done in 2D, but
xgvis allows layouts in arbitrary dimensions, 3D being the default. It
permits missing values, which can be used to implement multidimensional
unfolding.
It is used as follows:
o Start up with a user-supplied or random starting configuration.
o Initiate MDS optimization. As the optimization algorithm does its
work, observe both the changing stress values and the animated
point configuration.
o Examine the optimized configuration with 3D rotations and grand
tours and drill-down operations such as labeling and linked brush‐
ing.
o Enhance the configuration with glyphs, colors and lines for inter‐
pretation.
o Modifiy the dissimilarities, the stress function, and/or the con‐
figuration by
- transforming the dissimilarities
- choosing weights or cutting extreme dissimilarities
- restricting MDS to subsets
- hand editing the existing configuration or
- selecting a new random configuration
OPTIONS-dims n
Specify n, the dimensionality of the embedding space. By default,
its value is 3.
-stepsize x
Specify the initial stepsize; its default value is 0.1.
FILES
XGVis uses a set of input files with a common root (which we'll call
fname in the man page) and a suffix. First, each set must contain a
file with the suffix .edges, .dat or .dist.
fname.dist
Distance matrix: an n x n matrix, with entries separated by white
space and one row per line.
fname.edges
Line segments: specifications for the pattern of line segments which
connect pairs of points. The file must contain at least two numbers
per line. The first two numbers represent the row numbers of the two
points that should be connected. (This is exactly like the structure
of a fname.lines file in xgobi.) In addition, if a third number is
present, it is taken to be an edge weight.
If this line is present and the distance matrix is absent, then the
distance matrix is computed from it, with each edge representing a
distance of one.
fname.dat
fname.pos
Starting positions: an n x p matrix, with entries separated by white
space and one row per line.
If this file is present and a distance file is absent, the distance
matrix is computed from it.
fname.lines
Line segments: specifications for the pattern of line segments which
connect pairs of points. If this file is present, then the edges
file is used to create the distance matrix but the lines file is used
to draw the edges.
Many additional files can be specified. See the xgobi man page for
descriptions of fname.col (variable labels), fname.row (case labels),
fname.colors (glyph colors), and fname.linecolors (line colors), in
particular.
AUTHORS
Andreas Buja (andreas@research.att.com)
Deborah Swayne (dfs@research.att.com)
CONTACT
Deborah Swayne (dfs@research.att.com)
SEE ALSO
Sample data files are included in the XGVis distribution.
For papers and further pointers, check the following web page:
http://www.research.att.com/areas/stat/xgobi/
BUGS
Probably too numerous to mention, but you do the authors a favor if you
report the ones you notice.
20 November 1998 XGVis(1)
