Curvy Bump Chart

Get Data

Let’s start with some sample data of team performances over the years. Create an Excel spreadsheet and add the following data into a tab named Data.

Connect Data

Open up Tableau Desktop and connect to the spreadsheet in the Data Source page. Once the connection is done, drag the Data sheet from the left pane into the Canvas. The Canvas will now show the Data table which is at the logical layer. Double-click on the Data table to go to the physical layer of the canvas.

In this physical layer, we will be performing a Union of the data with itself. Now, drag the Data sheet from the left pane again to the bottom of the Data table until you see the Drag table to union option visible. Once visible, release the sheet to complete the Union.

After this task is done, you will see the Data grid showing the following result of the union along with two new columns added named Sheet and Table Name. The Table Name column will have two unique values Data and Data1 to showcase the two sets of data that are part of the Union.

Plot Basic Sigmoid graph

Before we dive deep into the chart, we will create a basic sigmoid graph. A sigmoid function is a mathematical function whose graph has a characteristic S-shaped or sigmoid curve. The mathematical formula for a Sigmoid is as follows,

$$ \sigma(x) = \frac{1}{1 + e^{-x}} $$

Let’s create the following calculated fields to recreate the above Sigmoid function in Tableau,

IF [Table Name] = 'Data' THEN 1
ELSE 49
END

INDEX()-1

([Index]-25)/4

1/(1+EXP(-[T]))

Steps to create the basic sigmoid graph,

1. Right-click on the Path field and then select Create and Bins....
2. In the Edit Bins [Path] pop-up menu, edit the Size of bins to 1 and select OK to close the menu.
3. Drag the newly created Path (bin) dimension onto the Rows shelf.
4. Right-click on the Path (bin) pill in the Rows shelf and make sure the Show Missing Values option is selected.
5. In the Marks card, change the Mark Type selection from Automatic to Line.
6. Drag the Path (bin) pill from the Rows shelf into the Path mark in the Marks card.
7. Drag the T measure onto the Columns shelf, and right-click on the pill and select Compute Using > Path (bin).
8. Drag the Sigmoid measure onto the Rows shelf, and right-click on the pill and select Compute Using > Path (bin).

We now have created our basic Sigmoid graph, that resembles an S-curve. Here we have used the Data Densification technique to add more data points using the Path dimension and the Show Missing Values feature to create a smooth curve.

Modify Sigmoid Graph

Now we are going to use some math and modify the Sigmoid function to slightly change the appearance of the graph. Update the following two existing calculated fields,

IF [Table Name] = 'Data' THEN 1
ELSE 201
END

(-6+([Index]-151)*6/25)

With the update, we have added additional data points to elongate the tail on the bottom left-hand side and accommodate a rounded bar chart that will overlap on the curve.

Create Calculated Fields and Parameter

We are now stepping into advance level of this visualization, for which we will need to create the following,

Parameter

Create a parameter named Distance with the Data type as Integer and Current value as 19.

Calculated Fields

LAST()

WINDOW_MAX(MAX([Score]))

WINDOW_MAX(MAX([Score]))

[Value]/[Max Value]*100

RANK_UNIQUE([Value],"desc")

LOOKUP([Current Position], 1)

IF [Index] < [Percentage] + [Distance] AND [Index] > [Distance] THEN 1
ELSE 0
END

IF [Last]=0 THEN 0
ELSE ZN([Next Position]) - ZN([Current Position])
END

IF [Index] < 151 THEN RANK_UNIQUE ([Value])
ELSE RANK_UNIQUE([Value]) + ([Sigmoid] * [Multiplier])
END

Create Ranked Rounded Bar Chart

We will now create a Ranked Rounded Bar chart for our visual to arrange the score as per Rank.

1. In the Columns shelf, replace T with Index, and right-click on the pill and select Compute Using > Path (bin).
2. In the Rows shelf, replace Sigmoid with Rank, and right-click on the pill and select Compute Using > Path (bin).
3. Drag the Year dimension onto the Columns shelf, and right-click and make sure it is selected as Discrete.
4. Drag the Team dimension into the Color section on the Marks card.
5. Right-click on Rank in the Rows shelf, and go to Edit Table Calculations
   • In the Nested Calculations dropdown, select Rank.
   • Set Compute Using to Specific Dimensions.
   • Ensure that only Year of Year and Team are selected below.
   • Arrange the order to Year of Year at the top, and Team below that.
   • In the Restarting every menu, select Year of Year.
   • In the Nested Calculations dropdown, select Last.
   • Set Compute Using to Specific Dimensions.
   • Uncheck all options in the Specific Dimensions sub-menu below.
6. Drag the Size measure to the Size section in the Marks card and,
   • Right-click on the Size pill and select Compute Using > Path (bin).
   • Right-click on the Size pill again and go to Edit Table Calculations.
   • In the Nested Calculations dropdown, select Max Value.
   • Set Compute Using to Specific Dimensions.
   • Make sure to check only Year of Year, Team and Path (bin).
   • Rearrange the order to Year of Year, Team and Path (bin).
7. Right-click on the Rank axis of the visualization and then Edit Axis...,
   • In the Scale section, select the Reversed option.
   • Close the Edit Axis menu.

In the above chart, the Teams are now properly ranked for each Year from top to bottom, with the length of the bar being a percentage of the Score compared to the Maximum Score in the dataset.

Create Curvy Bump Chart

Now that we have created the Sigmoid graph and Ranked Rounded Bar chart, we are going to link them up together to make our final visualization.

To combine them, Right-click on Rank pill on the Rows shelf and go to Edit Table Calculations

1. In the Nested Calculations dropdown, select Next Position.
   • Set Compute Using to Specific Dimensions.
   • Ensure that only Team and Year of Year are checked.
   • Arrange the order with Team at the top.
2. In the Nested Calculations dropdown, select Current Position.
   • Set Compute Using to Specific Dimensions.
   • Ensure that only Team and Year of Year are checked.
   • Arrange the order with Year of Year at the top.
   • In the Restarting every menu, select Year of Year.
3. In the Nested Calculations dropdown, select Last.
   • Set Compute Using to Table (across).
   • Close the Table Calculation menu.

We can additionally add custom shapes to the beginning of the bar chart to uniquely identify the teams. To achieve this,

1. Create the following Calculated Field to represent team logos in the visual.

IF ATTR([Path]) = 1 THEN [Current Position]
END

2. Drag the Logo measure to the Rows shelf and drop it next to the Rank pill.
3. Right-click on the Logo pill and go to Edit Table Calculations.
   • In the Nested Calculations dropdown, select Current Position.
   • Set Compute Using to Specific Dimensions.
   • Ensure that only Team and Year of Year are checked.
   • Arrange the order with Year of Year at the top.
   • In the Restarting every menu, select Year of Year.
4. Right-click on Logo pill on the Rows Shelf and select Dual Axis.
5. On the right of the visualization you will see an axis for Logo,
   • Right-click on the axis and select Synchronize Axis to align both the axes.
6. Go to the Marks card section and open up Logo mark card,
   • Remove the Size pill.
   • In the Mark Type dropdown selection, select Shape.
   • Drag the Team pill from the Logo mark card into the Shape, to change the Logo mark type to shape.

Although, it looks a bit messy, we have finally created a Curvy Bump Chart.

Cleanup

For our final step, we are going clean up the visualization.

1. Right-click on the Index axis at the bottom and then Edit Axis...
   • In the pop-up menu, for the Range select Custom.
   • In the Fixed start set the value as -10.
   • In the Fixed end set the value as 200.
   • Adjust these two values accordingly until you see the line chart being seamless.
2. From the menu bar at the top select Format > Borders
   • In the Format Borders menu that appears on the left select Columns at the top.
   • For the Column Divider section, set Pane to None.
3. From the menu bar at the top select Format > Lines
   • In the Format Borders menu that appears on the left select Sheet at the top.
   • Set Grid Lines to None.
   • Set Zero Lines to None.
4. Now hide the following two axes
   • Right-click on the Logo axis and unselect Show Header.
   • Right-click on the Index axis and unselect Show Header.

And there you have it, a Curvy Bump Chart visualization. You can update the logos by uploading your custom shapes to the dashboard.