A Graph Recreation in Tableau - Part 2: How To Build
I received a number of pings about yesterday's post showing the sankey-style slopegraph in Tableau (here). Here are the basics of the recreation using calculations in Tableau to simplify the process even further.
INSTRUCTIONS UPDATED 4/4/2014- Thanks to Tableau Zen Master Jonathan Drummey for pointing out that the previously used Xval field is not needed. It's now simply replaced with t.
To create this visualization I use the Sigmoid Function: S(t )=1/(1+e (-t ))
(more information here.)
In Tableau I use the function EXP(1) for e. So we need the input variable t. Therefore we need 4 fields.
State, 2012 Ranking, 2013 Ranking, t
To get the shape of the line I am going to plot 49 points for each state (49 was simply used to get enough points to plot the shape of the curves and is the same number of values in t ). t = a value between -6 and 6 in .25 increments (which is 49 values)
The data file is available here so you can load and follow along in Tableau. There are 3 extra fields in the Excel file to show the calculations, but they are not needed in Tableau.
Step 1: Open Tableau and Import Data
Step 2: Create some calculated fields
Calculated Field Name: Sigmoid Function
Calculated Field Name: Curve
Formula Updated 4/8/2014- Thanks to Catherine Rivier for offering a much more elegant solution than the original formula.
[2012 Ranking] + (([2013 Ranking]-[2012 Ranking])*[Sigmoid Function])
Calculated Field Name: Color
IF [Curve] <10.5 then 1
ELSEIF [Curve] <20.5 then 2
ELSEIF [Curve] <30.5 then 3
ELSEIF [Curve] <40.5 then 4
ELSE 5 END
Calculated Field Name: Size
Formula: ABS([2013 Ranking]-[2012 Ranking])
Step 3: Build the Viz
Move t to Columns
Move Curve to Rows
Move State to Details
Move t to Details and Convert to Dimension
Set Marks to Line
Edit X-Axis to Fixed with Start = -6.5 and End = 6.5 (the extra .5 allows room for the labels)
Edit Y-Axis and Reverse Scale
Move Size to Size
Move Color to Color
Edit Color using Stepped Color with 5 Steps
Uncheck "Show Header" on Y-Axis and X-Axis
Move State to Label
Select Left most points (at X = -6) and Select "Always Show" under Marks Label
Repeat for Right most points (at X = 6)
Format Curve to Number Format with 0 decimals
Move Curve to Label
Format Label to "<SUM(Curve)>. <State>"
Format Sheet Lines to remove Gridlines and Zero Line (set to "None")
Format Sheet Borders to remove border (Row Divider and Column Divider Pane to "None")
Format Font Style/Color and Viz Spacing as needed
Click Color on the sheet and set "Markers" to "None". This will remove the dots at the end points.
You should now have a visualization that looks like the example. Use ColorPic (free color tool) to get the colors just right and import into the Tableau Preference file using type="ordered-sequential" for this categorical color scheme.