Supply and Demand graph

I found an issue with this answer.  If the supply value is not the same from month to month then this process does not work.  The value of the supply stays constant because the date being used is from the Company table where the demand is at.  The matrix doesnt know that the values changed for the same date on the supply table.  I am trying to figure this out myself for my own data and having a heck of a time.