Custom geocoding in Tableau - Cell-by-Cell Formula Trace

Sample Data

This data represents a small custom geocoding table with city names and their latitude and longitude coordinates.

Cell	Value
A1	City
A2	Springfield
A3	Rivertown
A4	Lakeside
B1	Latitude
B2	39.78
B3	40.12
B4	38.95
C1	Longitude
C2	-89.64
C3	-88.45
C4	-90.12

Formula Trace

IF [City] = 'Springfield' THEN MAKEPOINT(39.78, -89.64) ELSEIF [City] = 'Rivertown' THEN MAKEPOINT(40.12, -88.45) ELSEIF [City] = 'Lakeside' THEN MAKEPOINT(38.95, -90.12) ELSE NULL END

Step 1: [City] = 'Springfield'

Step 2: MAKEPOINT(39.78, -89.64)

Step 3: [City] = 'Rivertown'

Step 4: MAKEPOINT(40.12, -88.45)

Step 5: [City] = 'Lakeside'

Step 6: MAKEPOINT(38.95, -90.12)

Step 7: ELSE NULL

Step 8: Complete IF statement evaluation per row

Cell Reference Map

    A          B          C
1 | City     | Latitude | Longitude |
2 | Springfield -> 39.78 -> -89.64 |
3 | Rivertown  -> 40.12 -> -88.45 |
4 | Lakeside   -> 38.95 -> -90.12 |

The formula uses the City names in column A to match and assign latitude and longitude from columns B and C.

Result

    A          D
1 | City     | Geo Point            |
2 | Springfield | (39.78, -89.64)    |
3 | Rivertown  | (40.12, -88.45)     |
4 | Lakeside   | (38.95, -90.12)     |

The result column D shows the geographic points created by the custom geocoding formula for each city.

Sheet Trace Quiz - 3 Questions

What does the MAKEPOINT function do in this formula?

A Returns NULL if city is unknown

B Checks if the city name matches

C Creates a geographic point from latitude and longitude

D Calculates distance between two points

Key Result

IF city name matches a known city THEN create geographic point with its latitude and longitude ELSE return NULL

Practice

1. What is the main purpose of custom geocoding in Tableau?

easy

A. To create charts other than maps

B. To change the color scheme of maps

C. To export maps as images

D. To add new or special locations not included in Tableau's default maps

Solution

1. Step 1: Understand Tableau's default map data

   Tableau has built-in locations but may miss some special or new places.

2. Step 2: Purpose of custom geocoding

   Custom geocoding lets you add these missing locations by providing coordinates.

3. Final Answer:

   To add new or special locations not included in Tableau's default maps -> Option D

4. Quick Check:

   Custom geocoding = add new locations [OK]

Hint: Think: Why add new places to a map? [OK]

Common Mistakes:

• Confusing custom geocoding with color or style changes
• Thinking it exports maps instead of adding data
• Assuming it creates non-map charts

2. Which file format is required to import custom geocoding data into Tableau?

easy

A. .csv (Comma-separated values)

B. .xlsx (Excel workbook)

C. .txt (Plain text file)

D. .json (JavaScript Object Notation)

Solution

1. Step 1: Identify Tableau's accepted custom geocoding format

   Tableau requires a CSV file with location names and coordinates for custom geocoding.

2. Step 2: Compare file types

   CSV is the standard for tabular data import in Tableau for geocoding, unlike Excel or JSON.

3. Final Answer:

   .csv (Comma-separated values) -> Option A

4. Quick Check:

   Custom geocoding file = CSV [OK]

Hint: Remember: CSV is simple table data for Tableau [OK]

Common Mistakes:

• Choosing Excel because it's common for data
• Thinking JSON or TXT are accepted for geocoding
• Confusing file formats for other Tableau features

3. Given this CSV snippet for custom geocoding:

Location,Latitude,Longitude
MyTown,40.7128,-74.0060
NewPlace,34.0522,-118.2437

What will Tableau do after importing this file?

medium

A. Show an error because coordinates are invalid

B. Replace all existing locations with MyTown and NewPlace

C. Add MyTown and NewPlace as mappable locations on Tableau maps

D. Ignore the file because it lacks population data

Solution

1. Step 1: Understand the CSV content

   The CSV has location names with valid latitude and longitude values.

2. Step 2: Tableau's behavior on import

   Tableau adds these locations to its map data without removing existing ones.

3. Final Answer:

   Add MyTown and NewPlace as mappable locations on Tableau maps -> Option C

4. Quick Check:

   Valid CSV adds locations [OK]

Hint: Valid coordinates + names = new map points [OK]

Common Mistakes:

• Thinking Tableau replaces all locations
• Assuming coordinates are invalid without checking
• Believing extra data like population is mandatory

4. You imported a custom geocoding CSV but Tableau does not show your new locations on the map. What is the most likely error?

medium

A. You forgot to restart Tableau after import

B. The CSV file has incorrect column headers like 'Lat' instead of 'Latitude'

C. Tableau does not support custom geocoding

D. The CSV file is too large for Tableau to process

Solution

1. Step 1: Check CSV format requirements

   Tableau requires exact column headers: 'Location', 'Latitude', and 'Longitude'.

2. Step 2: Identify common import issues

   Incorrect headers like 'Lat' cause Tableau to ignore the data.

3. Final Answer:

   The CSV file has incorrect column headers like 'Lat' instead of 'Latitude' -> Option B

4. Quick Check:

   Correct headers = data shown [OK]

Hint: Check headers match exactly: Location, Latitude, Longitude [OK]

Common Mistakes:

• Blaming file size without evidence
• Thinking Tableau lacks custom geocoding support
• Assuming restart is always needed

5. You want to map a new set of store locations in Tableau that are not recognized by default. Your CSV has duplicate location names but different coordinates. What is the best way to handle this in custom geocoding?

hard

A. Add a unique identifier to the location names to differentiate each location

B. Remove duplicates and keep only one coordinate per name

C. Import as is; Tableau automatically handles duplicates

D. Change all location names to the same name for simplicity

Solution

1. Step 1: Understand duplicate location issues

   Duplicate names with different coordinates confuse Tableau's mapping.

2. Step 2: Use unique identifiers

   Adding a unique ID or modifying names helps Tableau distinguish each location.

3. Step 3: Avoid data loss or confusion

   Removing duplicates or renaming all the same causes loss or errors.

4. Final Answer:

   Add a unique identifier to the location names to differentiate each location -> Option A

5. Quick Check:

   Unique IDs fix duplicate location issues [OK]

Hint: Make each location name unique to avoid confusion [OK]

Common Mistakes:

• Assuming Tableau auto-fixes duplicates
• Deleting duplicates losing data
• Using identical names causing map errors