I have a dual axis chart showing two line graphs. One line graph shows the sales by month and the other line graph shows a forecast of sales by month for a 12 month period. I have synchronized the graphs so they both appear on the same graph. I would like to filter the first graph so it only shows a few months of data. Does anyone know how to filter only one line graph in a synchronized dual axis chart, without effecting the other line graph? I tried creating a duplicate of the datasource as this thread suggested "https://community.tableau.com/thread/125595", but then I was unable to show both line charts on the same graph. My end goal is to show the first few months of the data and then the forecast for the whole year synced up on the same graph. Any tips are greatly appreciated.