To format zeroes (0) in Tableau to something else, such as a dash (-) for example, is simple using standard formatting techniques.

In the number formatting there’s a Custom option.

The syntax of this can be used to change 0 values to anything we want. The structure of the Custom number format is:

Positive;Negative;Zero

Enter the following in the Custom format to display all positive and negative values to 1 decimal place and convert all 0s to become a ‘-‘:

#,##0.0;-#,##0.0;

You can actually change zero values to anything you want using this technique. The Custom format #,##0.0;-#,##0.0; Zero Value gives the following: