Issues with data range and series panel in graphing a line chart for supply & demand

[zjlipson]

I am having trouble graphing two lines in a line chart. For example, in doing a simple supply and demand lined chart and a line for the equilibrium point, I have data for supply, demand, and price. I highlight the data and insert a line chart. I go to select data to attempt to edit the legend series and the horizontal category axis labels. After I highlight the correct x-values and correct y-values for my supply and then do the same for my demand, I get an error message that reads: "the data range is too complex to be displayed. If a new range is selected, it will replace all of the series in the Series panel.

I've never experienced this before. I'm very frustrated because I'm graphing a very simple supply & demand graph and then want to add a third line for the equilibrium supply and demand point.

I would greatly appreciate if someone could kindly help me with my issue.

 

[zjlipson]

I've answered my own question. The problem was that I was using a line chart instead of an X Y Scatter chart.
Most of the time, our excel errors are because of the rudimentary of things.