Scatter Chart Boundaries

[grime]

Not even sure how to explain this, but I'm going to give it a shot. I'm fairly confident in my VBA skills, but I'm not sure on the methodology to get what I'm after.

I'm trying to determine the points on a scatter graph that define the boundaries of that scatter graph.

An example might help illustrate by issue. I have the following 12 points:

1: 0, 1.5
2: 1, 5
3: 2.5, 5.5
4: 3, 6.2
5: 4, 5.5
6: 5.5, 5.8
7: 5.2, 2.5
8: 7, 0.3
9: 3, 2.5
10: 4.3, 1
11: 2.5, 0
12: 1.5, 1.3

If you graph them, you can visually see that points 1, 2, 4, 6, 8, 11 and back to 1 define the area.
scatter graph example image

So how do I do that? Any help would be greatly appreciated.

[Richard Buttrey]

Does the attached help.

It uses Data Filter Advanced to output all the plot points which have >= n-2 neighbouring co-ordinates for each of the x & y co-ordinates. Where n = the number of plots

i.e There are always at least 4 which are identified by the maximum and minimum co-ordinates. Then there could in theory be an infinite number of other points. These are any points where there are at least n-2 neighbours. In this example these are points 2 & 6.

HTH

[Andy Pope]

VBA solution. Set the TightFit property to true.

http://www.andypope.info/charts/convexhull.htm