Intersection

  • Thread starter Thread starter Derick C.
  • Start date Start date
D

Derick C.

How can I calculate the intersection point in Excel where two parabolic
curves intersect? Take the following data as an example:

Y1 22 22 21 21 20 19 16
Y2 15 15 17 18 21 25 29
X 0 43 86 129 171 214 257
 
How can I calculate the intersection point in Excel where two parabolic
curves intersect?
Click to expand...

This is a mathematical question, not an Excel charting question. Perhaps
sci.math can help.
 
Derick,
Still it may be an Excel task, if your numbers determine not exact function
values, instead they are more or less random, and the “parabolasâ€, e.g. the
2nd order curves, should only fit their order (“trend†in economics). Then
you must first obtain the parameters axx of both parabolas y = a01 + a11.x
+ a21.x.x, and y = a02 + a12.x + a22.x.x. How to do that, you can learn from
the help to the Excel function LinEst. The second step is to extract x of the
intersection by setting both right sides equal. Here you must solve the 2nd
order equation. This is a fine exercise in Excel based on your elementary
school knowledge. The stylish Excel variant of this step is using Solver,
which you can apply easily with higher order curve fittings.
Good luck
 
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