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Friday, 8 October 2010

Why don't people like bullet charts? Part 1

From speaking with users and report writers, I have found that there are a number of aspects of bullet charts which people might find a bit off-putting. On the other hand, there are users and report writers who love bullet charts and 'ra ra' them as far as possible, using them to replace pie charts and gauges.This blog is the first in a series, which aims to give airtime to the reasons that I've heard given by business users and report writers for disliking bullet charts. I will blog about one reason at a time, since I have heard a few different perspectives and it is always worth exploring different points of view. My own opinion is that bullet charts are a good way of displaying data that allows you to make the most out of the 'real estate' on your dashboard or report. This was the intention of Stephen Few when he devised the bullet chart, and I have found them useful in a number of projects for different customers. 

However, when I've been working with business users and report writers, I have found that, for some people, it can be a struggle to understand bullets. For them, it is the easier option to stay in the 'comfort zone', sticking to more familiar charts such as pies. I think it is worthwhile exploring the reasons that people give for disliking bullet charts. I would like to address these reasons individually as part of a series, so I can try to find ways to help users to make the transition from not understanding bullet charts, to making an informed decision regarding whether bullet charts are right for them in particular circumstances. Here, I would like to talk a bit about just one of these issues, which is the role of colour in bullet charts. There are other reasons, and these will be covered in subsequent blogs. 

One reason that people can get put off bullet charts is, I think, simply the colours of the samples that you find on the internet. For example, I have had feedback from some report business users that the colour of the sample bullet charts is a bit heavy on the eyes, and they do not like it.  Here is an example from wikipedia:
Bullet_graph_labeled

In our modern world with colour printers, users often expect 'nice' colours rather than black and grey. I completely understand that Few is trying to make the bullet chart as simple as possible for the human visual system to assimilate, and to also take into account the impact of colour-blindness. However, from speaking with people who see bullet charts for the first time, I think that the heavy black line is not visually pleasing.
In Reporting Services 2008 R2, a bullet chart control is available, which is highly customisable. This means that you are not restricted to using heavy black and grayscale colour schemes. I'll show you to do this in a future blog, but in the meantime, here is another example of a bullet chart, which is the basic bullet chart provided in SSRS 2008 R2, with no customisations or data:
4.BaseBullet

The lighter grey effect is less harsh than a lot of the bullet chart samples that you can find on the internet. Here is another sample bullet chart. It does not have any data since I don't want to distract you from the main theme of the impact of colour on producing visually-pleasing bullet charts. Here, we use different intensities of blues this time:
SSRSTableSoFarBaseBlue

This sample was produced using SSRS 2008 R2, and the blue colours were chosen using Color Brewer, which is aimed at helping you to choose the most appropriate colours for your particular visualisation. It's produced by Cynthia Brewer at Penn State University, and it's been such a great find that I had to pass on the tip!
There will be more on bullet charts in the future, so watch this space! To summarise, I think that the sample bullet charts can be a bit off-putting because they make use of black and grey. In SSRS 2008 R2, however, it's easy to change the colour, which has quite a big impact on producing visually-pleasing bullet charts in a way that is not at the expense of user understanding.
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