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Re: Inflection Point Detection
From: |
Ben Abbott |
Subject: |
Re: Inflection Point Detection |
Date: |
Mon, 14 Mar 2011 21:34:30 -0400 |
On Mar 14, 2011, at 8:59 PM, aegreen wrote:
> Can't seem to figure this out but I assume it's a common problem.
>
> I have a data set that contains an inflection point between two linear
> equations. For example producing a graph as follows:
>
> ^
> | /
> y | /
> |_______/
> |
> <------------------> x
> |
> |
>
> Has any one had success or knows of a technique to use octave to determine
> the inflection point in this line?
>
> Thanks,
>
> AG
One approach would be to use mkpp, ppder, and ppval. I haven't tested this, but
...
pp = mkpp (x, y);
pp2 = ppder (ppder (pp));
d2y_by_dx2 = ppval (pp2, x);
n = find (abs (d2y_by_dx2) == max (abs (d2y_by_dx2)));
x_inflection = x(n)
Ben