I just uploaded an improved workbook to the Dropbox folder. I hope this makes things clearer.

Shared with Dropbox

www.dropbox.com

It also includes some questions about the difference between line and scatter plots, which I clearly don't understand.

I added this explanatory text to the sheet:

All of these graphs are based on the same data range (C4:I11) which is for blood glucose reading charts.

C & D contain the dates of the readings for X axis labels.

E & F contain the PM & PM readings in mg/dL for X,Y plots.

G-I contain band widths for stacked area plots showing the ranges of readings that are low, normal, and high.

The objective is to get the combo graphs (A2, B2, & C2) that show where the readings (AM & PM) fall in the three ranges (Low, Normal, & High). This is accomplished by using line or scatter plots for the readings and stacked area plots for the range bands.

Before I knew about combo plots, I would insert a chart of all one type and then change the ones that needed to be changed. This brought to my attention some oddities in the horizontal axes of the initial charts (A1, B1, & C1).

If I start by inserting either a line plot or a stacked area plot, the horizontal axis shows both the dates and the days. But if I start with a scatter plot, it starts with counting numbers. It was my understanding that scatter and line plots would behave just the opposite. Scatter plots, being X,Y plots, would use the first column as the independent variable (X) and the rest as the dependent variables (Yi), whereas line plots always treat all columns as Y values. If you select any of the first 6 graphs (A1, B1, C1, A2, B2, & C2), the highlighting in the table seems to indicate that columns C & D are the independent variable and the rest (E-I) are the dependent variables.

Curiously, if I select only the Date column (D) and not the Day column (C), then both the line and stacked area plots use the date as the independent variable (A3, A4, B3, & B4).

I would love it if someone could explain what is going on to me.