Comments on: Be Careful with the Y-Axis… https://depictdatastudio.com/be-careful-with-the-y-axis/ Tue, 14 Jan 2020 18:55:02 +0000 hourly 1 https://wordpress.org/?v=7.0.2 By: AndrĂ© Petras (@anmipe) https://depictdatastudio.com/be-careful-with-the-y-axis/#comment-554 Tue, 06 Oct 2015 18:16:08 +0000 http://annkemery.com/?p=7248#comment-554 In reply to Jessica Schillinger (@JessSchillinger).

I totally agree with Jessica here. Please don’t truncate the y-axis when using bar charts. Plot a line chart instead.

]]> By: boB Rudis (@hrbrmstr) https://depictdatastudio.com/be-careful-with-the-y-axis/#comment-553 Tue, 06 Oct 2015 17:14:11 +0000 http://annkemery.com/?p=7248#comment-553 Wouldn’t this be a case for possibly not even using a bar chart and just stating the there was virtually no variation in youth enrollment from 2008-2014? (the coefficient of variation for this data set is ~1.3%). Unless there is some threshold # (i.e. 26,500) that the data “needs” to be at (which you could then draw a line at as a performance indicator regardless of the y-axis), this may be a talking point sentence vs a chart.

]]> By: Jessica Schillinger (@JessSchillinger) https://depictdatastudio.com/be-careful-with-the-y-axis/#comment-552 Tue, 06 Oct 2015 15:23:54 +0000 http://annkemery.com/?p=7248#comment-552 I would say that your options are great rules, but would disagree with your visual metaphor of a bar chart.
Bar charts inherently use length to visualize the measure of the data. If you truncate the length at all, the visual metaphor disappears all together, regardless of whether or not the axis is labeled.
A better visual metaphor in this case (and I would say of any case in which the axis is truncated) would be a trend line chart. The data in the case are already over time, making it the more appropriate choice from the start. Then, if you need to truncate the axis to make the change in the data more clear, you don’t lose the meaning of the visual metaphor, like in the case with the bar chart.
In line charts that are truncated, I like to not only indicate the scale with labels, but also distinguish the baseline with weight. For example, if I normally make the baseline a solid, 1pt line and the grid lines 0.5pt dotted line, I would also code the “baseline” in a truncated chart the in the same way as I would the rest of the grid lines. I’ve found this has helped people more readily notice that the baseline is not really a baseline, but a truncated y-axis.

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