# Thursday, May 5, 2011

Look at the four series of data below.

I II III IV
x y   x y   x y   x y
10 8.04   10 9.14   10 7.46   8 6.58
8 6.95   8 8.14   8 6.77   8 5.76
13 7.58   13 8.74   13 12.74   8 7.71
9 8.81   9 8.77   9 7.11   8 8.84
11 8.33   11 9.26   11 7.81   8 8.47
14 9.96   14 8.1   14 8.84   8 7.04
6 7.24   6 6.13   6 6.08   8 5.25
4 4.26   4 3.1   4 5.39   19 12.5
12 10.84   12 9.13   12 8.15   8 5.59
7 4.82   7 7.26   7 6.42   8 7.91
5 5.68   5 4.74   5 5.72   8 6.89

Is there a pattern to the data in each series? How do the series relate to one another? It’s difficult to answer these questions looking only at the raw data.

However, if we display the data as 4 scatter graphs on the same page (Figure 1a), we can quickly see the pattern in each series and we can use that pattern to predict the next value in the series. We can also see outliers in series III and IV and ask questions about why those outliers occur.

 
[Figure 1a]

Figure 1a is a good representation of the data because it allows us to understand the data quickly and easily and because it answers questions and sparks follow-up questions about the data.

As a software developer, I spend a lot of time writing software to maintain data. There are many tools and training to help us store, update data and retrieve data. But few people talk about the best way to present data in a meaningful way.

Professor Edward Tufte of Yale University is one person who is doing research in this area and writing about it. Tufte studied graphical representations of data to find out what makes an excellent visualization and what problems occur in data visualization. He has written several books on the topic, describing guidelines to follow and common traps to avoid. In my opinion, his best book on this subject is The Visual Display of Quantitative Information (ISBN 0961392142).

This series will review Dr. Tufte ‘s research, ideas and conclusions on Data Visualization.

Over the next couple weeks, I’ll explore excellent charts created throughout history and identify what makes them so excellent; graphs that lack integrity and serve to mislead the viewer; and some guidelines that Dr. Tufte suggests for improving data visualization.


This is an ongoing series discussing the research of Dr. Edward Tufte on Data Visualization.

Thursday, May 5, 2011 4:31:00 PM (GMT Daylight Time, UTC+01:00)