Color-blindness – why does it happen, and how can data visualisations help?

How people perceive colour is an interesting issue. The Young-Helmholtz Trichromatic theory of vision proposed that we have red/green/blue receptors, which are then combined to show different colours.  It is thought that the red-green receptors are close together, and perhaps this is the root of the issue. Needless to say, the issue is complex but interesting.
According to popular wisdom, it is thought that the red-green chromatic channel developed in order to provide an evolutionary advantage for determining ripe fruits against a background of foilage. Tell that to your children, next time they refuse to eat fruit! However, this ‘ripe fruit’ theory has been difficult to observe in field studies. One group of researchers conducted field studies in black-handed spider monkeys, and found that luminance contrast was just as important in distinguishing fruits. If you’re interested to read more, here is an interesting study that illustrates the complexities of perception, which involves the field study of primates. On the other hand, a separate study showed that trichromatic primates found it easier to determine and select ripe fruits, and you can find more information here.
How does this impact data visualisation? It is possible to produce visualisations that make the most of luminosity in order to encode values, along with the size of the data point, in order to convey the message of the data visualisation. Another issue is that determining colour and luminosity can be a subjective issue, and point size may help to provide additional cues. I envisage it as if it is the detection of fruit in viticulture. Therefore, one winemaker might ascertain that a grape’s optimal point of ripeness is at one point, and another viticulturist might determine that the ripeness point is at another point in time. Similarly, it isn’t always easy to ask experimental subjects to ascertain the amount of ‘greenness’, ‘redness’, or ‘blueness’ of a point. There has been some work in computer vision, aimed at distinguishing the RGB in fruit, which is interesting to read.
It is suggested that about 12% of males are colour-blind, which means that they are restricted from using the red-green channel. If you are interested in reading more about the experience of a colour-blind person, please do read this entertaining blog by Geoffrey Hope-Terry.
To summarise, data visualisations can therefore augment understanding by assisting the perceptual processes involved in luminance and the blue-yellow colours. It is also possible to use the size of the data point to convey the message of the data. In other words, data visualisations should aim not to exclude members of the audience by including lots of red and green together.

SQLPass Business Intelligence Virtual Chapter References and Slides

Thank you to everyone who attended my SQLPass Business Intelligence Virtual Chapter webinar! I have lots of questions to follow up, from both during and after the event. Please watch this space for more responses to questions over the next few days, and I will try to ensure that I answer every question. The slides are at the bottom of this blog post.

I’ve provided references below to some of the Data Visualisation people and material that I mentioned today. I hope that these are useful to you.

Ben Schneiderman – Ben’s Eight Golden Rules of Interface Design is an interesting read. In the presentation, I refer to one of Schneiderman’s essays, “The Eyes have it.” The guideline is summarise -> zoom and filter -> details-on-demand, and is known as the ‘Visual Information-Seeking Mantra’. 

Stephen Few – Stephen has written a number of books, which you can find at his site – there is a wealth of information there! If you’re a fan of data visualisation, then you should consider his blog, Perceptual Edge, a must-read. In particular, I’d like to shout out the following books:

Malcolm Gladwell – Malcolm has a great deal of interesting things to say on a whole range of topics, and I’m never going to be able to introduce him properly. 

Hans Rosling – What I love about Rosling’s work, is that he highlights health and social factors, poverty and health. This is data visualisation in action, to help people in poor circumstances – the sort of people who cannot always read what is written about them. He promotes a ‘fact-based’ world view on these issues. The YouTube video of Rosling’s data visualisation is below, which was made by BBC4. 

I should add that I’m not in any way associated with this video – but I get asked about it a lot, so I’ve embedded it here from YouTube. 

Here are the slides from today. I look forward to your comments, and I will answer the remaining questions in due course.


Tiny correction to MSDN Blog – adding report server content types to a Sharepoint Library

I spotted a small error in MSDN article entitled Add Report Server Content Types to a Library (Reporting Services in SharePoint Integrated Mode) It’s just a tiny error, but small enough that someone looking for it, might run into problems. The second half of the document should read:

To add report server content types

1.Open the library for which you want to add Reporting Services content types.

2.On the Library Tools ribbon tabs, click the Library tab.

3.On the Settings ribbon group, click Library Settings.

4.Under Content Types, click Add from existing site content types.

5.In the Select Content Types section, in Select site content types from, click the arrow to select Reporting Services. << This should actually say ‘SQL Server Reporting Services Content Types. Please see the image below:

SQL Server Reporting Services types
6.In the Available Site Content Types list, click Report Builder, and then click Add to move the selected content type to the Content types to add list.

7.To add Report Model and Report Data Source content types, repeat steps 5 and 6.

8.When you finish selecting all of the content types that you want to add, click OK.

I hope that helps someone out.

Find the missing sessions in the 2011 SQLPass Summit DVD set

Is everyone enjoying their newly-minted 2011 PASS Summit DVD set? I am, you betcha! Some of the sessions are missing, though. 
The following sessions are missing from the 2011 PASS Summit DVD:
Application and Database Development
Working With XML in SQL Server
Kendal Van Dyke, Insource Technology
SQL Azure
This Ain’t Your Father’s Cloud
Buck Woody, Microsoft and Kevin Kline, Quest Software
BI Architecture, Development and Administration Topics
Common Analysis Services Design Mistakes and How to Avoid Them
Devin Knight, Pragmatic Works
BI Client Reporting and Delivery Topics
End-user Alerting with SQL Server Code Name “Denali” Reporting Services
Lukasz Pawlowski, Microsoft
To stream the sessions, please go here.
You will need your PASS Summit username and password to access the sessions. If you don’t have a login, then you should sign up! SQLPass offer tons of great, free SQL Server training. With SQL Server 2012 on the horizon, you don’t want to miss out!