Graphing error in grapher software

Hi,
I am creating different 2D scatter plots graphs, where each graph has multiple plots on it (about 20 plots per graph). The plots come from the same excel worksheet, where the different plots are defined as sections of rows within the worksheet. Unfortunately, there is not always data available in the sections referenced by the different plots .I do not know why Grapher would do this?Is this an error in Grapher, a changeable setting, or a flaw in my approach?
Thanks.
