Software
There are many choices for statistical software at various
levels of technical skill and ease of use. The American
Statistical Association (ASA) Section on Statistical Computing
has put together the following listing: http://www.amstat.org/careers/statisticalsoftware.cfm. It describes features and benefits for some
common and specialized packages.
Graphics
What makes statistical packages distinct from business
software or commercial computer languages is the availability
of analytic graphics tools. These graphical methods are
not just for illustration. When graphs are designed with
appropriate methods, they let the viewer extract relationships
between levels, identify anomalies, simplify the complex,
and make better decisions.
Charts and graphs, which once required manual drawing
and then specialized programming, infuse all of daily life
now. Web sites and print publications on all subjects casually
provide illustrations with data. Free’analytics’
software is abundant. In offices, Powerpoint
®
slides filled with bar and pie charts are expected with
any table of numbers, perhaps pulled from 3-click EXCEL®
graphs.. But how often do people consider the advantages
and disadvantages of EXCEL defaults like a grey background
crossed with thick lines? For all of the choices of color
and shape, there is little thought put into what the graph
encodes and what the viewer can glean from the flashy display.
In the past 25 years several thinkers have emerged to
address the graphics quandary.
Edward
A. Tufte, Professor Emeritus of Yale, has published
4 ‘coffee-table’ books that explore how data
and images can connect. A true Renaissance man, he uses
examples from Gallileo, the Napoleonic wars, fish ecology,
aerodynamics, and contemporary sculpture. He is known for
coining the phrase ‘chartjunk’ and his tirade
against bullet-point style Powerpoint
® presentations.
(Wired Magazine, September 2003). William
S. Cleveland, formerly of Lucent/Bell Labs and now a
professor at Purdue University, wrote two more pragmatic
books, The Elements of Graphing Data and Visualizing
Data. Since their publication, the concepts have spread
to other texts and software manuals.
Tufte and Cleveland advocate ‘small multiples’,
displaying many graphs of each level of a category on one
page or screen. Cleveland was involved in the development
of the S language at Bell Labs. A classic example of ’small
multiples’ from Visualizing Data and The
S-Plus User’s Guide, is the barley yield data
below.
Each site for the planting is a separate panel on the
trellis. There are 10 varieties labeled on the side of the
panels. The red and blue are yields for different years.
Trellis graphs can be used to show any kind
of category. A type of trellis is a subject plot. A subject
offers a visual story than can be hidden when only looking
at averages and statistical tests.
The freeware version of the S Language, R,
has emerged as the de-facto standard for statistical research
- www.r-project.org.
The commercial S-version, S-PLUS is available from TIBCO
Software, Inc.
Spotfire,
another product recently acquired by TIBCO, goes even further,
perhaps to the extreme.
The five graphs above in a tiled display show the results
of a drug screening for a cancer compound that should inhibit
tumor growth. Clockwise, the tile combines a bubble plot,
a three-D graph with response by color, a trellised heat
map that looks at 9 plates at once, a segmented histogram,
and a two-D plot with response by color. The power in an
active SPOTFIRE session is to select out data simultaneously
in the displays, dig deeper into sections with the slider
bars, and make discussing large data more productive.
Books
Every year publishers hope that the new textbook will become
the definitive book. The book is definitive for you if it
helps you better understand concepts. Older texts often
are clearer with more details on statistical tests and concepts.
They serve as the basis for much of recent work. However
they can be obsolete regarding computation and graphics.
Contact us at 201-673-4301
if you want to discuss a book for yourself and your team.
