This is the first in a series of 10 posts where I’ll suggest a (hopefully) coherent set of tips to improve our charts and, more important, to improve the way we make sense of the data. These are the planned posts:
- General charting;
- Column/Bar charts;
- Line charts;
- Scatterplots (XY charts);
- Pie charts;
- Other chart formats;
- Dynamic charts;
- Miscellaneous tips;
- Bonus post: online resources.
These will be very short tips, and I’m sure some of them will require further explanation. In time, all of them will be properly linked to a more detailed post (that will keep me off the streets for a while…). This is a kind of road map for the next few months and, when finished, a (partial) table of contents for the blog.
So, general tips on charting:
- A chart shows trends, patterns, outliers; if you already strive to make them apparent, you don’t need to read the next 99 tips…;
- Do you really need a chart? Sometimes the task and the data suggest another method of data analysis;
- Know your audience. If your audience is uncomfortable with some formats your message will be lost;
- Make sure you have enough data to create a pattern (two data points are not enough to create a trend line);
- Make sure you don’t have more than enough data: just because you have it, you don’t have to show it…; keep removing interesting data until only relevant data for your problem remains;
- A chart should be able to answer elementary, intermediate and global questions regarding the data;
- Don’t assume that the charts you see in the media are the ones you need to run your business;
- Learn how to lie with charts and, of course, avoid those lies;
- Let the reader see related charts simultaneously;
- Chart overload is as bad as information overload.
It’s your turn, now. What are your best tips in this category? Please share them in the comments (if you have specific tips please save them for the next posts). I believe that Tufte’s principles (avoid chart junk, maximize data/ink ratio, high data density…) are already implicit in some of these tips.