All fields in a data source have a data type. The data type reflects the kind of information stored in that field, for example integers (410), dates (1/23/2015) and strings ("Wisconsin"). The data type of a field is identified in the Data pane past i of the icons shown below.

Data type icons in Tableau

Icon Data blazon
Text (string) values
Appointment values
Date & Fourth dimension values
Numerical values
Boolean values (relational only)
Geographic values (used with maps)
Cluster Group (used with Find Clusters in Data(Link opens in a new window))

You can change the information blazon for a field either on the Data Source page or in the Data pane.

Change the information type for a field in the Data Source page

Sometimes Tableau incorrectly interprets the data type of a field. For example, Tableau might interpret a field that contains dates as an integer data blazon, rather than a date data type.

You can modify the data type for a field that was part of the original data source (as opposed to a calculated field created in Tableau) on the Data Source page.

  1. Click the data type icon for the field (as shown in the table above).

  2. Cull a new information type from the drop-downward listing:

Tip: Exist certain to change data types before you lot create an extract. Otherwise, your data may not be accurate. For case, if a floating-point field in the original data source is interpreted every bit an integer by Tableau, and you create your extract before you change the field's data type, the resulting floating-point field in Tableau will have some of its precision truncated.

For data on changing data types on the Data Source page, see Data Source Page.

Change the data blazon for a field in the Information pane

To modify the data blazon of a field in the Data pane, click the icon to the left of the field name, and so cull a new data type from the drop-downwards list.

Change the data type for a field in the view

To change a field's data blazon in a view, correct-click (control-click on a Mac) the field in the Data pane, cull Change Information Type, and then select the advisable data type from the drop-downward list.

Notation: Sometimes the data in your database is more precise so Tableau tin can model. When you lot add these values to the view, a precision alert appears in the right corner of the condition bar. See Condition Bar Information.

Mixed data types in data from files

Most columns in a Microsoft Excel, Microsoft Access, or CSV (comma-separated value) file contain values that are all of the same data type (Booleans, dates, numbers, or text). When you connect to the file, Tableau creates a field in the appropriate area of the Data pane for each column. Dates and text values are dimensions, and numbers are measures.

However, files that you connect to might include columns that have a mixture of information types, such as numbers and text, or numbers and dates. When y'all connect to the file, the mixed-value column is mapped to a field with a single data blazon in Tableau. Therefore, a cavalcade that contains numbers and dates might exist mapped as a number information type (making information technology a measure out) or it might be mapped as a date data blazon (in which instance Tableau treats information technology as a dimension.)

Tableau determines how to map mixed-value columns to data types by the information types of the showtime 10,000 rows in an Excel data source, and the start 1,024 rows in a CSV data source. For example, if about of the get-go 10,000 rows are text values, the unabridged column is mapped to use the text data type.

Note: Empty cells as well create mixed-value columns because their formatting is different from text, dates, or numbers.

When Tableau determines a data type for each field, if the values in a field don't match that data type, Tableau handles the field in one of several different ways, depending on the data type. For example, sometimes Tableau populates those fields with Nada values, as shown in the following tabular array:

Mapped data type Treatment of other data types in the field.
Text Dates and numbers are treated as text. Nulls are not created.
Dates Text is treated as Aught. A number is treated every bit the day in numeric order from i/1/1900.
Numbers Text is treated every bit Zilch. A date is treated as the number of days since i/1/1900.
Boolean Text, dates, and numbers are treated as Null.

If using fields that are based on mixed-value columns introduces difficulties when analyzing your data, you tin can do one of the following:

  • Format empty cells in your underlying data source and so that they match the data blazon of the cavalcade.

  • Create a new column that does not comprise the mixed values.