If you saw the 2020 Iron Viz, one of the winners, Christian Felix, created a stunning visualization with lines across a map (listed here). It looks like a Sankey diagram pointing to locations on a map.
I recreated the below visual for a Starbucks dashboard where I added navigation buttons to switch the dashboard from a dark theme to a light theme (located here).
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I found a delightfully easy to follow video on how to recreate this Sankey map on youtube by Amit Bhat here. I modified the steps and have them listed below;
You will need to prepare your data a certain way for this visual.
I created an excel spreadsheet with three tabs, titled Data, Densification and Coordinates.
Here is a preview of the Data tab.
I added a column called Join and put the text "Link" in it. I then copied this cell all the way to the end of the country list.
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In the same Excel workbook I added another spreadsheet called Densification.
I created a column called Join and a column called Point. In the Join column I put the word "Link" and pasted this all the way down to row 101. In the column called Point, I entered the data 1-100. Row 2 containing the number value of 1 and then row 3 containing 2, all the way down to row 101 with the value of 100.
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The last worksheet I needed to create in this Excel workbook was called Coordinates. Here I had columns called Country Name, Longitude and Latitude.
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In Tableau I put data worksheet onto my data pane. I then connected it to the Coordinates sheet by dragging it onto the data pane and then I connected the data tab to the Densification data set.
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On my Worksheet in Tableau I needed to make sure Latitude and Longitude had a Geographic role. I did this by right-clicking on the icon next to the metric, selecting Geographic role and then clicking on the matching name.
(You may need to get this from Country Name through the drop-down settings) I also made sure they were Dimensions and Decimal number (not strings).
I needed to create the following Calculated Fields;
Start X
CASE [Ownership Type]
WHEN 'Licensed' THEN 45
WHEN 'Company Owned' then -75
When 'Franchise' then 127
WHEN 'Joint Venture' THEN 150
END
*This separates the Sankey into the 4 start points
Start Y
90
* You can enter a negative number here if you want the start point to be at the bottom leading to the top.
# Point
100
Sigmoid
1/(1 + EXP(0.2)^ -(([Point]-([# Point]+1)/2)+([Latitude]-[Start Y])/([# Point]-1)))
*Latitude needs to be a number or this calculation won't work.
Curve X
[Start X] + ([Longitude]-[Start X]) * [Sigmoid]
*Make this a geographic role and assign Longitude
Curve Y
[Start Y] + ([Point]-1) * ([Latitude] - [Start Y]) / ([# Point]-1)
*Make this a geographic role and assign Latitude to it.
Arrow
IF [Point] = 100 THEN 100
ELSE 0
END
First I placed the Curve X calculated field onto the Columns shelf. I right-clicked on this pill and selected Dimension.
Then I placed the Curve Y calculated field onto the Rows shelf and made sure it was formatted as a Dimension.
Once I did this the Sankey visualization started to form;
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I changed the Chart type on the Marks card from Circle to Line.
I put Ownership Type onto the Color Marks card.
I then placed Country Name onto the Detail Marks card.
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To add the arrows at the bottom of the lines I put another Curve Y calculated field onto the Rows shelf.
I made sure it was formatted as a Dimension, and selected Dual Axis.
On the second Marks card for Curve Y. I put the Arrow calculated field onto the Shape Marks card.
For the 0 value I used a Blank shape. For the 100 value, I selected the down arrow. In this previous blog I mentioned 3 shapes you should have, with Blank being one of them.
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Now the only arrow that should appear will be at the bottom of the line.
If you want to make the start lines appear closer together, simply modify the Start X calculated field.
Modified Start X
CASE [Ownership Type]
WHEN 'Licensed' THEN 0
WHEN 'Company Owned' then -25
When 'Franchise' then 25
WHEN 'Joint Venture' THEN 50
END
Here's the image with the modified calculation above;
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You can put an over lay above the map on your dashboard. I created a separate worksheet with a Stacked Bar Chart for the different Ownership Types.
I also modified my Maps using the Map menu in Tableau.
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