I hope someone can help because I'm starting to hate charts. I'm basically trying to add an average line to my line-graph by using calculated averages instead of the trend-line tool.

I have two tables. Table 1 has Column A (a number) and Column B (also a number). I've created a line graph of this table using Column A as the x-axis (horizontal) and Column B as the data points.

I have another table that calculates the averages of Column B if Column A falls within a certain range. 
=AVERAGEIFS(B2:B10,A2:A10,">="&E3,A2:A10,"<="&F3)
(simplified code since that's not the point of this post.)

I want to add this line to the chart. It's basically the same as adding a trend line, except I need to have the calculated number since the ranges vary. I calculated the median of the ranges and used that as my x-axis and the averages as my data points.

The result:
Screen Shot 2017-10-05 at 7.35.37 PM.png

The average line is the blue one. I think the issue is that I only have 20 or so "average" data points and thousands of the other data points. But I don't understand why the average line doesn't stretch across the graph since I've used the median of the ranges and those fall all along the x-axis (ie if I have an x-axis that goes from 1-10 and I plot points at 3, 5, and 7 I would think it should stretch out.)

Note: I also plan to find the minimum of each average range and add that as well (but I will use a formula to find the exact point that instance happens rather than the median of the average range). So I hope the solution works in both instances.