Amount of Vaccines assigned to Department by Lab - Circular Sankey Diagram

juan.rozo23's Avatar

juan.rozo23

08 Sep, 2021 03:44 PM

Hi everyone!

I want to visualize the amount of vaccines assigned to each Department by Lab, I have the idea to visualize this information in a "double circular Sankey"(See Image). I have followed this very useful post http://support.nodebox.net/discussions/nodebox-2-3/5977-trying-to-create-a-sankey-diagram shared by Rob and john, and I found a couple of challenges. 1)In the data that I have, some departments("States") have received a massive amount of doses from a given lab at one time(560.000) and others have received a minuscule amount of doses from the same given lab(170). Therefore I haven't been able to find how to keep a reasonable proportion between them, I have tried the increase the number in the divide node but the small numbers just disappear if i divide them too much. 2) I want to have two circles. One inner circle representing the labs and the amount of vaccines per lab(Might be a donut chart) and the outer circle represents each to the 27 departments. How can I make the connection between the inner circle and the outer circle happen, without duplicating the departments ?

Cheers,

Juan

  1. Support Staff 1 Posted by john on 09 Sep, 2021 02:25 AM

    john's Avatar

    Juan,

    Before tackling this problem you might want to take a step back and think hard about what you are trying to communicate here.

    When one Sankey line is 3000 times thicker than another, there is no way to rigidly follow this proportion and make both understandable at the same time. Some possible alternatives:

    • You could group the smaller dose lines into an "Other" bucket instead of trying to show each dose line separately at the same time. If need be, you can add a separate donut showing how that one "Other" bucket breaks down into a dozen small departments/labs. In other words, just show the major trends in your Sankey and break the edge cases into a separate chart.

    • Instead of making the thicknesses directly proportional to the totals, you could bucket them into 3 or 4 categories: big, medium, and small. A key would explain that thick lines represent doses of more than 100K, small (but still visible) lines represent doses of less than 1000, and medium lines represent everything in between. This would prevent viewers from seeing the true relative sizes between different departments, but would allow them to clearly see a simpler, more fundamental pattern (e.g. that that are two major departments, a few medium size players, and all the rest negligible.). That may be all you really need to communicate; it depends on your audience and what questions they are trying to answer with your visualization.

    • A compromise between direct linear scaling and bucket categories is to use a logarithmic scale. Instead of dividing totals by a constant to get thickness, take the square root or (other fractional power) first. And choose settings so that the smallest value is still visible. This way you are still showing relative proportions, but the biggest lines are only 10 or 20 times thicker than the smallest, not 3000 times.

    I am skeptical of your idea to wrap sankey lines from each donut wedge to all the many departments. No matter how you do this, there will be too many lines, most of them very thin, and all of them wrapping around and getting on top of each other. You will probably just make a big hairball that is impossible to understand.

    Again: what questions will this visualization answer? What patterns are you trying to convey? You should play with the shape of your data and then answer these questions deeply BEFORE deciding on the best visualization technique.

    Instead of a winding donut sankey hairball, you might consider a trellis instead. That is, make a chart of small multiples, with maybe a separate lab donut for each department. When you arrange these donuts in a grid with consistent coloring it makes it possible to investigate each department on its own terms while at the same time seeing larger patters between departments.

    Another form of trellis would be to make a separate Sankey for each lab and simply arrange those sankeys from top to bottom from bigger labs to smaller. If you use the same thickness scale across all sankeys (maybe using logarithmic
    scale) then the overall proportions will be visible at a glance but details of the smaller labs will still be discernible.

    Think hard about these possibilities before you commit to one design. Then see how far you get, and if you're still stuck post your draft and I'll see if I can help.

    Good luck!

    John

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