MATLAB: Extract turning, angles, or “unsteady” points in a Plot

corner detectionedgeextremaoptimizationturning points

Hello Community,
I have a set of coordinates obtains from some sensor readings. The plot of the given data can give graphs such as those depicted on the image on the Graph below:
http://i.stack.imgur.com/NzCWd.jpg http://i.stack.imgur.com/kmnya.jpg
Can anyone please advise me on a method I could use to detect the "turning" points indicated in red. Please note that I do not have the actual function of the curve, just some set of (X, Y) coordinates. I was thinking of an algorithm that may for example for each point coordinates, would check the positions of surrounding points to find out whether or not the current point was one of those "special" point. Any help, or even some directions towards a possible solution would be greatly appreciated.
Thank You

Best Answer

Yanick: We had this question come up recently in http://www.mathworks.com/matlabcentral/answers/57194. I used Roger's method (one of the naswers) to come up with this demo: http://www.mathworks.com/matlabcentral/answers/57194#comment_118587. It should work great in your case.
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