Creating a Gantt Chart over time with summed bar

Question

I have data that looks like this:

name    date    count
a   11/10/2012  2
a   12/10/2012  3
a   13/10/2012  2
b   12/10/2012  6
b   13/10/2012  2
b   14/10/2012  3
c   14/10/2012  2
c   15/10/2012  2

And I want to create a bar chart that has the sum of the count on the y axis and time on the x axis. The width of the bar should be the length of the time, like a Gantt chart. Each name has its own bar. Here is an image that shows what I am after.

The bars should overlap if the times overlap.

I have tried various things in Tableau but haven't really got close.

Is this kind of chart possible in Tableau? If not in 7, will it be in 8? I have heard it makes it possible to create some more complex chart types.

Answer 1

The trick with Gantt charts in Tableau is to put a calculation on the size shelf that calculates the duration of each bar in units of days. See the example screenshot at Tableau example

You also need a continuous date field on the columns shelf to get a horizontal time axis.

In this example, I also did a few more optional things, such as, turned off aggegation under the analysis menu to get a mark per data row, rather than aggegating them, added a discrete date to the rows shelf to make each bar go on a different line (as long as each bar starts on a different date) and hid the column for that start date.