Dual-axis maps in Tableau - Cell-by-Cell Formula Trace

Sample Data

Sample data showing cities with their latitude, longitude, sales, and profit values used for creating dual-axis maps in Tableau.

Cell	Value
A1	City
B1	Latitude
C1	Longitude
D1	Sales
E1	Profit
A2	New York
B2	40.7128
C2	-74.006
D2	100000
E2	20000
A3	Los Angeles
B3	34.0522
C3	-118.2437
D3	85000
E3	15000
A4	Chicago
B4	41.8781
C4	-87.6298
D4	60000
E4	12000

Formula Trace

Dual-axis map layers: Layer 1 = Map with city locations (Latitude, Longitude), Layer 2 = Circle marks sized by Sales and colored by Profit

Step 1: Plot points using Latitude and Longitude for each city

Step 2: Create first axis with map background and city points

Step 3: Create second axis with circle marks sized by Sales

Step 4: Color circles by Profit values

Step 5: Synchronize axes and overlay second axis on first

Cell Reference Map

    A          B          C          D          E
1 | City     | Latitude | Longitude | Sales    | Profit   |
2 | New York | 40.7128  | -74.0060 | 100000   | 20000    |
3 | Los Angeles | 34.0522  | -118.2437| 85000    | 15000    |
4 | Chicago  | 41.8781  | -87.6298 | 60000    | 12000    |

References:
- Latitude (B2:B4) and Longitude (C2:C4) for map points
- Sales (D2:D4) for circle sizes
- Profit (E2:E4) for circle colors

This map shows which columns are used for plotting city locations and which columns control circle size and color in the dual-axis map.

Result

    A          B          C          D          E          F
1 | City     | Latitude | Longitude | Sales    | Profit   | Map Output
2 | New York | 40.7128  | -74.0060 | 100000   | 20000    | ●●●●● (large, bright)
3 | Los Angeles | 34.0522  | -118.2437| 85000    | 15000    | ●●● (medium, medium bright)
4 | Chicago  | 41.8781  | -87.6298 | 60000    | 12000    | ●● (small, less bright)

Legend:
- Circle size ~ Sales
- Circle color brightness ~ Profit

The final dual-axis map shows city points with circles sized by sales and colored by profit, layered on the same geographic map.

Sheet Trace Quiz - 3 Questions

Which columns provide the geographic location for the city points on the map?

A Sales and Profit

B Latitude and Longitude

C City and Sales

D Profit and Latitude

Key Result

Dual-axis maps overlay two map layers sharing the same geographic scale, combining location points with sized and colored marks.

Practice

1. What is the main purpose of using dual-axis maps in Tableau?

easy

A. To layer two map types for better comparison or detail

B. To create a 3D map visualization

C. To filter data based on geographic regions

D. To export maps as images

Solution

1. Step 1: Understand dual-axis maps concept

   Dual-axis maps combine two map layers in one view to show more information.

2. Step 2: Identify the main use

   This layering helps compare or add details like points over filled areas.

3. Final Answer:

   To layer two map types for better comparison or detail -> Option A

4. Quick Check:

   Dual-axis maps = layering two map layers [OK]

Hint: Dual-axis maps layer two map types in one view [OK]

Common Mistakes:

• Thinking dual-axis maps create 3D maps
• Confusing dual-axis maps with filtering
• Assuming dual-axis maps export images

2. Which of the following is the correct way to create a dual-axis map in Tableau?

easy

A. Create two separate worksheets and combine them in a dashboard

B. Drag one geographic field to Columns and filter by region

C. Use the 'Show Me' panel and select 'Pie Chart'

D. Drag two geographic fields to Rows and then right-click one and select 'Dual Axis'

Solution

1. Step 1: Identify how to create dual-axis maps

   In Tableau, you drag two geographic fields to Rows or Columns, then right-click one and choose 'Dual Axis'.

2. Step 2: Eliminate incorrect options

   Filtering or using 'Show Me' pie chart does not create dual-axis maps; separate worksheets are not dual-axis maps.

3. Final Answer:

   Drag two geographic fields to Rows and then right-click one and select 'Dual Axis' -> Option D

4. Quick Check:

   Dual axis = right-click axis > Dual Axis [OK]

Hint: Right-click axis and choose 'Dual Axis' to combine maps [OK]

Common Mistakes:

• Trying to create dual-axis maps via filtering
• Using 'Show Me' for map layering
• Combining worksheets instead of dual-axis

3. Given two map layers: one showing filled states and another showing city points, what happens if you do NOT synchronize the axes in a dual-axis map?

medium

A. Tableau will automatically merge the layers perfectly

B. The two layers may not align correctly on the map

C. The map will show only one layer

D. The map will display a blank view

Solution

1. Step 1: Understand axis synchronization

   Synchronizing axes ensures both map layers use the same scale and position.

2. Step 2: Consequence of not synchronizing

   Without synchronization, layers may shift and not align properly, causing visual mismatch.

3. Final Answer:

   The two layers may not align correctly on the map -> Option B

4. Quick Check:

   Unsynchronized axes = misaligned layers [OK]

Hint: Always synchronize axes to align map layers correctly [OK]

Common Mistakes:

• Assuming Tableau auto-aligns layers without sync
• Thinking map shows only one layer if unsynced
• Believing unsynced axes cause blank maps

4. You created a dual-axis map but the points layer is not visible on top of the filled map layer. What is the most likely cause?

medium

A. The points layer is hidden behind the filled map layer

B. The marks card for the points layer is set to 'Circle' with zero size

C. The layers are not synchronized

D. The data source is disconnected

Solution

1. Step 1: Check layer order in dual-axis maps

   In dual-axis maps, one layer can hide another if it is on top and opaque.

2. Step 2: Identify why points are invisible

   If points are hidden behind the filled map layer, they won't be visible even if present.

3. Final Answer:

   The points layer is hidden behind the filled map layer -> Option A

4. Quick Check:

   Layer order affects visibility in dual-axis maps [OK]

Hint: Check layer order if points are invisible [OK]

Common Mistakes:

• Assuming unsynchronized axes hide points
• Thinking zero size circle is default
• Blaming data source without checking layers

5. You want to create a dual-axis map showing sales by state as filled areas and customer locations as points. Which steps ensure the map layers align and display correctly?

hard

A. Drag State to Rows, Customer Latitude and Longitude to Rows and Columns, create dual axis, then do NOT synchronize axes

B. Drag State to Detail on one Marks card, Customer Latitude and Longitude to Rows and Columns, create dual axis, then synchronize axes

C. Drag State to Color, Customer Latitude and Longitude to Rows and Columns, create dual axis, then synchronize axes

D. Drag Customer Latitude and Longitude to Rows and Columns, create dual axis, then filter by State

Solution

1. Step 1: Assign State to Color for filled areas

   Using State on Color fills the map areas by state, showing sales distribution.

2. Step 2: Use Customer Latitude and Longitude on Rows and Columns

   These geographic fields plot customer points on the map.

3. Step 3: Create dual axis and synchronize axes

   Dual axis layers the filled states and points; synchronization aligns them correctly.

4. Final Answer:

   Drag State to Color, Customer Latitude and Longitude to Rows and Columns, create dual axis, then synchronize axes -> Option C

5. Quick Check:

   State on Color + Lat/Long + dual axis + sync = correct map [OK]

Hint: Use State on Color and synchronize axes for correct layering [OK]

Common Mistakes:

• Putting State on Detail instead of Color
• Not synchronizing axes after dual axis
• Dragging State to Rows instead of Color