Typical Map Errors and How to Deal With Them
The tableau is designed to make the most of geographical data, so you can get to the “where” as well as the “why.” With instant geocoding, Tableau automatically turns the location information you already have into maps which are rich and interactive with 16 levels of zoom—or use custom geocodes to map what matters to your business. In the visual environment of Tableau, you can explore the world through data and share what you find in just a few clicks.
However, it is sometimes not unusual to have some missing or erroneous data, especially when you are investigating a table for the first time. Fortunately, Tableau helps you identify non-conforming details and make corrections quickly without having to edit the data source directly. Figure 5.7 shows a filled map. The color encoding of the map displays the relative sales value of each state. You can see that there is something wrong with the view because Missouri is blank. This could be caused if an abbreviation was used for Missouri (MO) if the other state names are not abbreviated.
In the lower right area of the map in figure 5.7, there is a gray pill that includes the text (1 unknown). This indicates that one geographic record is missing or unrecognized in the data set. Clicking on the pill opens the special values menu that provides three options for dealing with the unknown record:
Figure 5.7: Filled map missing data
Clicking the edit location option exposes the special values menu you see in the upper left area of figure 5.8
Figure 5.8: Correcting place name errors
Selecting the Edit Locations’ option exposes the menu on the right of Figure 5.8. Tableau identified that the state of Missouri is misspelled. This is why there is no color fill for Missouri in the map. Fixing the error is done by typing the correct spelling into the “matching location” area. After typing a few letters, Tableau narrows the list of candidates to Mississippi or Missouri. Selecting Missouri aliases the state name in Tableau with the correct spelling and fixes the problem. The source data set is still wrong, but Tableau’s name alias will correct the problem in the map. Lock in the change by clicking the OK button. Tableau recognizes different place name variations (abbreviations) and will edit other geographic entities as well (city, county, province, etc.). This ability to quickly identify and correct non-conforming records will save you time and make it easy for you to provide detailed feedback to correct errors in your source data.
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