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Envisioning Information
Practicals
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Practical Sessions
The practical sessions will introduce
us to a range of useful visualization tools.
First we shall look at three useful tools for simple graph
visualization. Gnuplot is a simple plotting package which is
freely available on all UNIX systems. R is a powerful statistical
package, again available free, with versions on linux and Windows; it
includes some useful statistical plotting facilities. Finally
Microsoft Excel is of course a well known spreadsheet tool, but note
that it contains a wide range of charting facilities. There are
worksheets below to introduce you to gnuplot and R.
Once you have studied the worksheets,
there is the following exercise. The average rainfall for Leeds
(measured at Hollies Park) is available on the Web; find it and use
gnuplot, R and Excel to plot the data, taking care over the
visualization design. Compare the systems in terms of ease of
use, and effectiveness at presenting data. Find somewhere nearby
where there is average temperature data. Use the three systems to
create a visualization of temperature and rainfall for this region.
Our next session will look at
xmdvtool. This is an excellent tool for multivariate
visualization, with scatter plot matrix, parallel coordinates, glyphs
and dimension stacking. It is freely available from the xmdvtool web site, which also
includes a description of the software and many papers written by the
xmdvtool team. The creator of xmdvtool is Matthew Ward, with help
of many of his collaborators. Here is a simple worksheet:
xmdvtool
In week 3, we shall tackle a real
multivariate analysis problem as a
challenge.
Week 4 has been a break... but in
week 5 we shall start to look at scientific visualization....
For scientific visualization, we shall
look at a powerful visualization system
It is a Modular Visualization
Environment,
in which we connect modules together using visual programming. At
Leeds, we host the IRIS
Explorer
Centre of Excellence. For this practical, go to that site and
look in particular at Tutorials. Work your way through the first
UNIX IRIS Explorer tutorial. To help you in understanding the basic
concepts, Marcelo Cohen has
prepared this additional
page. Once you have
completed that
successfully,
move on to the second tutorial.
IRIS Explorer is available on both Windows and Linux.
Once you have worked through the
first
two tutorials, it is time to try a medical
imaging challenge.
We are now ready to tackle 3D visualization. Here is an extension
of the last challenge to provide a 3D
medical imaging challenge.
If you would like to practise with xmdvtool, look at the 'acorns'
dataset. Explore how the size of the acorn depends on the region
from which the oak tree comes. Can you find any other intersting
facts? Look at:
http://davis.wpi.edu/xmdv/datasets/acorns.html
If you want something hard, here is an astronomy
challenge.
To gain experience with IRIS Explorer for flow problems, try the
following. Use ReadLat to read in some flow data, from the file
${EXPLORERHOME}/data/lattice/flowpath.lat. Pass the data to the
NAGAdvectAnimate. This module will calculate the path of a set of
particles released into the flow from a 'box'. Connect
NAGAdvectAnimate to Render in order to display the particles. It
is also useful to include a WireFrame module in order to see the
boundary of the region. Try varying the position and size of the
box from which the particles are released - a good start for this is
position (1.5, 1.5, 1.5) and size (3,3,0.25).
Can you draw an isosurface of the velocity magnitude?
Ken Brodlie
December 2006