You will want to un-pivot your data so the structure changes from:
Make and model December 2010 January 2011 February 2011 Honda Odyssey 9,950 12,271 12,288
Make and model Month Sales Honda Odyssey Dec-10 9950 Honda Odyssey Jan-11 12271 Honda Odyssey Feb-11 12288
and that will allow you to easily create the attached.
See http://www.tableausoftware.com/support/knowledge-base/preparing-excel-files-analysis for additional details, and a link to download an Excel Add-In that transforms data.
monthly.twbx 12.1 KB
Thanks Joe! It makes pretty good sense now. I redid every step to make sure I figured out what you were doing, and it works fine now. So, the trick is also to make sure you have the data defined correctly as well (MM-YY and the like), eh?
I'll parse all the data and see what happens, and I'll get back to you if I have any more questions. Thanks again!
You will likely want your date fields formated like: "1/1/2011" instead of "Jan-11", that was just Excel choosing a poor default, and I did not take the time to correct it.