Too many axes

Posted to Design  |  Tags: ,  |  Nathan Yau

Kaiser Fung talks about the suck of overlaying plots to show a relationship.

When the designer places two series on the same chart, he or she is implicitly saying: there is an interesting relationship between these two data sets.

But this is not always the case. Two data sets may have little to do with each other. This is especially true if each data set shows high variability over time as in here.

This seems to happen a lot when people take the data-to-ink ratio too literally or they’re trying too hard to be clever within a given space. Overlays work on occasion, but I can’t think of any that did off the top of my head. Most of the time it’s better to split up the layers into multiple charts.

1 Comment

  • At every job post-MBA (I know, I know…) I’ve had to create slide after slide of these inane charts showing Value X and some ratio (growth, unit price, etc.) on the same time series. The purpose is apparently to show executives all the data in one place (data density!), not necessarily to highlight any interesting trend. Of course, the data density point is limited by the fact that these charts must be static for printing and most 8×11 slides can only include one such chart (one story per slide!).

    99.99% of the time, there is no interesting trend (much less any predictable trend going forward). I’ve tried a few times to point out the lack of value in such charts. But the standard response is “we agree with you, but this is what they’re used to seeing, so we need to keep producing it.” Of course, nobody has ever asked these senior executives what they’d prefer to see; it’s just taken as a given since the time of Henry V.



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