Excel-how a graph interprets blank cells

I have a spread sheet that produces some graphs. Some of the graphs are keyed off cells that use formulas to create the value. The problem is that even though I have selected “interpolate” for how the graph interprets a blank, it recognizes blank cells as a zero value and places them on the graph as such. I know there are ways around it, (“hide” those columns, etc) but this forces me to do a lot of maintenance on a lot of charts! Is there a “bug” in my software, or is this a deficiency inherent in Microsoft Excel?