Amy’s trendline was based on 12 months of X data and 8 months of Y data. Big deal, right? In 2003 it is no big deal, but in 2007 this seems to confuse the trendline.

When I extended the Y values to include four blank cells, the trendline still was goofed up. It turns out the chart was treating blank cells as zeros, and the trendline had a crazy slope to fit the four zeros at the end of the series. When I changed the setting to leave a gap in place of empty cells, the trendline behaved as expected.

My chart is set up as follows:

primary x axis – quarterly net income results (4 points) refecting 2008 and 2009 data
secondary x axis – horizontal bands to reflect tolerances (12 points)

This has worked great. The problem arises when I try to forecast the remainder of 2009. I would like to forecast based on the monthly data points I have (which is why the secondary axis is based on 12 points) I added this data and had this data be reflected as a line graph (vs the area stacked data which is currently on the secondary axis). I can add the trend and it works…until I save the file and close out. When I go back into the graph, my trend is still there but the projection is different – almost like it is taking into account different data.

I would be glad to provide the set up of my data and chart if needed, would really appreciate any help you could provide.

Thanks!