Gantt Bar Mark

The Gantt Bar mark type is useful for viewing dates, project plans, or the relationships between different quantitative variables. Tableau displays your data using Gantt bars when:

• The Mark menu is set to Automatic and you place one or more dimensions on either the Columns shelf or the Rows shelf, and then plot the dimensions against a continuous quantity.
  
• You select Gantt Bar from the Mark menu.
  

The distinguishing characteristic of Gantt Bars is that the length of every mark is proportional to the measure placed on the Size target.
The view below displays a dimension as a function of a continuous date. If the Mark menu is set to Automatic, the data would be displayed using bars. Selecting Gantt Bar and adding additional fields will display a view like the following.

In particular, placing the Days to Ship measure on the Size target causes every bar in the view to be drawn with a length that indicates the delivery time of an order. Additionally, placing the Ship Mode dimension on the Color target causes each bar to be colored according to the ship mode.
To try a hands-on exercise for building a Gantt Bar chart, see Building Gantt Bar Charts.