# #MRA_FOC #MRX Effective Data Visualization by Naomi Robbins, Part #2

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After a really neat bag lunch, it was time to jump back into part 2 of Naomi’s data visualization session. So many fun tidbits this afternoon and here are just a few.

• Banking to 45 degrees is something to consider – Choose a scale so that the angles within a chart are around 45 degrees. Neato!
• You can create charts without a zero but you need to have a good reason, e.g., if the chart with zero fails to show a change in slope. But your audience needs to have an understanding of how to read a chart without zero. BUT, bar graphs ALWAYS need zero because they are a judge of length which always starts at zero.
• People are confused by double Y axes, particularly if it’s the same variable on both sides. A double axis is where the right side of your chart uses one scale, e.g., from 0 to 10, and the left side of your chart uses another, e.g., from 0 to 20.
• Naomi has called a textbook publisher to complain that its charts were rife with chart lies. Let’s see if the next edition takes heed.
• Scary – people using textbooks with bad and misleading charts are usually designed for people who have no exposure to charts before. Publishers want the charts to be fun and engaging. Sad, sad, sad.
• Cindy Brewer has a great website on choosing colours for maps and it works great for charts as well. http://www.colorbrewer.org
• Sequential hues are good for sequential data (e.g., time series) – light blue, medium blue, dark blue. Diverging hues are good for categorical data – red, green, blue
• 8% of male population and 0.5% of female population has trouble with colour so reconsider the use of red and green in charts even if you use red to represent positive/go and negative/stop. Check your individual charts at www.vischck.com. VERY cool.
• Blue and orange are better colours for charts because there are fewer problems for people reading them.
• Graphs are for the forest, tables are for the trees. Tables are not better than graphs and graphs are not better than tables. Use the tool for the purpose.
• In 2010, no one is impressed that you can change a font (that’s just stupid) or make a 3d chart in excel.

If you haven’t been to a charting class before, you really should try Naomi’s course. You will learn far more tidbits than you can possibly remember but you will definitely learn something that you can implement immediately. I’ve taken the Tufte course and even I learned some new things. Yay charts!

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Any errors in representation are my own.

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