I'm trying to compare two three sets of data with line chart. However, two of them have the same x-axis values (Weeks) while the third set can be a different time period, so it might have more weeks or fewer (or occasionally, the same amount). I would like the third set skewed so that all lines start and finish at the same point (so the slopes can be compared visually). Is there any way to do this (I only need one y-axis)?

Thanks!

Jay