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Edward Tufte agrees with you: Baselines In general, in a time-series, use a baseline that shows the data not the zero point. If the zero point reasonably occurs in plotting the data, fine. But don't spend a lot of empty vertical space trying to reach down to the zero point at the cost of hiding what is going on in the data line itself. (The book, How to Lie With Statistics, is wrong on this point.) For examples, all over the place, of absent zero points in time-series, take a look at any major scientific research publication. The scientists want to show their data, not zero. The urge to contextualize the data is a good one, but context does not come from empty vertical space reaching down to zero, a number which does not even occur in a good many data sets. Instead, for context, show more data horizontally! . -- Edward Tufte, October 18, 2001
http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0... |
Ugh, the more I read of Tufte the less I like him. He loves to make blanket statements (like calling a point "wrong") in an authoritative way, and he's amassed enough adoring followers that people repeat his words like gospel instead of calling him on it.
It's valid to say that a non-zero-based scale shows the data better. But it's also completely valid to note that non-zero-based scales can be used in alarmist ways to make data extremely misleading.
I thought "The Visual Display of Quantitative Information" was terrible, and I went in really wanting to like it: http://www.amazon.com/review/R11NYC3OE3LBE