Tuesday, August 8, 2017

Log scale for XY charts

From now on, charte.ca supports log scale in all XY charts (bubble, scatter, motion). Consider the following visualization of World Bank and SIPRI Military Expenditure Database data:

Why log scale? There are a few cases when a log scale is appropriate. The most well known is: log scales allow a large range to be displayed without small values being compressed down into bottom of the graph. Consider the same visualization made using linear scale (this is just a screenshot, not an interactive chart, but it gives you a good idea about the problem):

As you see, X-axis outliers (India and China) and Y-axis outliers (Middle East states) make the rest of the pack crowd in the bottom left corner of the chart, making the whole chart unusable. Of course, if your goal is to stress the fact that India and China has huge population, or you want to make Middle Eastern countries military budget look even more impressive, you may want to use linear scale. It's totally up to the chart designer which scale to use.

As usual, a quick hint on how to import flat series data to charte.ca. After pasting raw data from the spreadsheet mentioned above, on step two of the import wizard, I made the following selections:

Enjoy the power of log scale.

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