In chart design it’s good to make things simple, but you certainly should avoid oversimplification. As Einstein said:
"Things should be made as simple as possible, but not any simpler"
Seth Godin presented in his blog The three laws of great graphs:
1. One Story
2. No Bar Charts
3. Motion
Effective chart design rules are simple, but reducing it to this set of 3 rules certainly is an over-oversimplification.
Particularly rule 2 is flawed. Seth details rule 2:
"NO BAR CHARTS
Bar charts are dramatically overrated, primarily because they’re the first choice in many graphing programs.The problem with bar charts is that they should either be line/area charts (when graphing a change over time, like unemployment rates) or they should be a simple pie chart (when comparing two or three items at the same scale).
Jorge, Kaiser and Jon already wrote some critical posts about this rule, where Jon suggested to replace rule 2 with
Choose Chart Types Intelligently
We are working tightly together with Stephen Few on a new product that helps business users creating effective charts with Excel and are therefore we are quite familiar with Stephen’s design principles.
Its an easy to learn set of rules
1. Determine the relationship you want to display
| Relationship | Sample |
Value Comparison | Sales in different regions |
Ranking | Best selling products |
Time-Series | Sales in the last 12 months |
Part-to-Whole | Market shares |
Deviation | Revenue Actual vs Budget in the last 12 months |
Distribution | Support response times |
Correlation | Relationship between employee’s heights in inches and their salary |
2. Determine if you want to emphasize individual values or the overall pattern
3. Determine the chart type
| Relationship | Encoding Method | |
Value Comparison | Bars and Columns |
|
Ranking | Bars and Columns |
|
Time-Series | Lines to emphasize the overall trends or pattern |
|
| Points connected by lines to slightly emphasize individual values |
|
| Columns to emphasize and support comparisons between individual values |
|
Part-to-Whole | Bars and Columns |
|
Deviation | Lines to emphasize the overall shape of the data |
|
| Points connected by lines to slightly emphasize individual data points |
|
| Bars and Columns to emphasize individual values |
|
Distribution | Columns to emphasize individual values |
|
| Lines to emphasize the overall shape of he data |
|
Correlation | Points and a trend line in the form of a scatter plot |
|
Armed with this set of rules you would rule out Seth’s pie chart, and use the bar chart in the appropriated business context.
Chart Type Selection Guidelines. I like this. It’s simple, yet detailed.
That’s strange, I can see your little graph icons in the RSS feed, but not in the actual blog.
That is exactly the problem that Seth is after.
I mean, it is very reasonable and following this would solve a lot of problems in chart design for printed publications and reports.
but presentations are a whole different matter.
on a slide, you want to convey one message. your graph must NOT carry any information that can be interpreted differently than the point you are trying to make. the corollary is that in virtually all cases, you should display as little data points as possible: 1 if possible, 2 but no more than 3. If you need more than 3 data points, use handouts.
now the problem with bar charts is that they remain legible even with many data points, so typically you would see slides with 5, 10 or more bars, which make the slide a less effective presentation means. And the author thinks they’ve done nothing wrong because they used a chart like the textbook says and not a pie chart which is always wrong.
Then, you see what Seth is meaning.
I fully agree that bar charts are not good for time series. who wouldn’t. but trying to cram too much info on one slide which is what bar charts encourage you to do is not the right answer.
“We are working tightly together with Stephen Few on a new product that helps business users creating effective charts with Excel”
Can you provide more information about the new product, sounds very interesting.
Regards,
Jose
Jose,
We will very soon post about Chart Tamer on blog.xlcubed.com.
Andreas