Line graph with two data sets

[Giordano Bruno]

I have a graph which tracks two sets of percentage values by weeks on the x axis. The data is in two adjacent columns and works well if I have multiple rows of data. I use code to set the data source using a dynamic range. If I remove all rows other than the first, the chart shows two points on week 1 and the other weeks. If I then rerun the data source macro, the chart changes to show only week 1 and the two points for the data. If I then rerun the code, the chart shows weeks 1 and 2 and a line between points 1 and 2.
It seems that the graph has assumed that when there is only a single row, there is only a single series and two weeks rather than the reverse. If anyone can point to a way forward I would be eternally grateful.