I love simple, effective data visualisations, and Eva Murray completely nailed that for #MakeoverMonday this week. Here is Eva’s viz:

Poles are no pole position for solar eclipse

It’s a bit good – I can’t think of anything I would change, and I liked it so much that I thought I’d write about exactly what needs to be done to recreate this viz. It’s pretty simple and much of the flourish is reserved for crisp design and formatting, rather than hugely technical Tableau wizardry. There are two sheets, one for the chart, and one for the Size legend.

Here is how the chart sheet is structured:

Screen Shot 2017-08-22 at 19.15.49

On Columns, Eva placed a calculated field, which simply converts the existing [Duration in seconds] field into minutes. No prizes for guessing this calculation:

Screen Shot 2017-08-22 at 19.17.08

The aggregation of the Latitude could be MINIMUM, MAXIMUM, MEDIAN, SUM or AVERAGE, it doesn’t matter in this instance as the derived value would be the same when the unique ID of [Eclipse ID] is on Detail. Once these fields are on Rows and Columns, and you stick [Eclipse ID] on Detail, you are welcomed by a dotty blue display:

Screen Shot 2017-08-22 at 19.20.52.png

Note the formatting of the [Duration (minutes)] field? Nice and easy:

Screen Shot 2017-08-22 at 19.21.44.png

Eva also has a couple of Filters in play. The viz is focused on total eclipses, so that option is selected from the [Eclipse type category]. Also excluded via a filter are eclipses with 0 duration.

So we have the bare bones already, how did Eva achieve the colour effect that she did? A calculation making use of the ABS() function:

Screen Shot 2017-08-22 at 19.24.52

So eclipses in locations with a negative latitude will simply have their negative values converted into positives. The calc in all its glory is:

Screen Shot 2017-08-22 at 19.31.06

Why do this? Well, without it you’d have a range of latitude values from 88.5 to -88.0, and you’d end up with this:

Screen Shot 2017-08-22 at 19.32.38.png

ABS() effectively ensures that inversions of latitude are basically treated the same, and so  you get a colour legend like this:

Screen Shot 2017-08-22 at 19.34.04

What’s next? [Duration (minutes)] on Size further highlights that the longer total eclipses occur closer to the equator. The sizing of that had to be manually adjusted on the resultant slider to get things just right on the dashboard, but that’s all.

The next visual features are the horizontal lines denoting the North Pole, Equator and South Pole. You could create calculations for these, but there’s absolutely no point. Eva took the most efficient route: Constant reference lines:

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A bit of formatting to differentiate the Poles from the Equator (to match the [Colour] calculation), and that’s more of less it – just the tooltips to check out now. Here’s what they look like:

Screen Shot 2017-08-22 at 19.49.24

Clean and simple – and with a minor twist. The duration now is depicted in terms of hours, minutes and seconds, to give more precision than is on the x-axis. Arguably the hours are redundant given the maximum duration is 7 minutes and 29 seconds, so perhaps that’s a change I would make. Here’s how Eva created this additional field:

Screen Shot 2017-08-22 at 19.51.15

With 86,400 being 60 seconds * 60 minutes * 24 hours in a day. This is formatted thus:

Screen Shot 2017-08-22 at 19.52.29.png

And, for completeness, the tooltip itself is structured as shown below:

Screen Shot 2017-08-22 at 19.53.13.png

Onto the Size legend, which has its own worksheet, built as follows:

Screen Shot 2017-08-22 at 19.55.28.png

Observant readers will note an additional Filter – [Eclipse ID]. This is required to limit the  “legend” to show three different sized circles, reasonably evenly distributed, so it looks right on the final dashboard. This took some tinkering and flicking to and from from the dashboard, to make sure things weren’t too crowded.

Once that’s done, it’s onto the final step of pulling things together on the dashboard. It’s a 1000×800, with only two really notable design flourishes – the two floated elements. First is a floated text box up beside the North Pole reference line, and the second is the custom legend and its corresponding annotation:

Screen Shot 2017-08-22 at 20.11.18

It’s basically the legend worksheet and a text box in a floating, horizontal container. After a year and a quarter with Tableau, I’ve finally started paying attention to containers!

And that, as they say, is “it”. I think it’s a fabulously clean viz and it remains my favourite #MakoverMonday submission of the week. It’s also wonderfully simple to break apart and rebuild, and I’d urge anyone looking to boost their Tableau experience and skills to take a look, so they can see how easy it can be to create a visually stunning dashboard without too much effort.

My attempt at recreating Eva’s viz is here:

Dashboard 1

 

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