How can I do to analyze a curve from scope

I need to calculate the exact inflexion point of my curve from the scope on simulink.

How can I do that?

this is my curve:

http://imageshack.us/f/198/calcularparmetros.png/

Thanks

Answer 1

[Walter Roberson]

You cannot calculate the exact inflection point. Calculating the exact inflection point would require either knowing the generating equations exactly, or require an infinite number of data points.

Remember, "inflection point" is an idea in the mind of The Calculus, and The Calculus is woeful and wrath about being misused for situations that are not continuous.

You could calculate approximate derivatives and use that to find points that are adjacent to an inflection point, but you cannot locate the exact inflection point.

Answer 2

[Fernando Loyola]

All right, thanks for that response, but you know how can I calculate an aproximate inflection point?

Thanks

Answer 3

[Walter Roberson]

I do not know what you would have to do in order to get access to the graph from Simulink. At the MATLAB level, once you have the figure handle you can find the axes handle, and from there, find the line or lineseries object; and then you can get() the XData and YData properties of the line.

After that, the first approximate numeric derivative is

approxFirst = diff(Y) ./ diff(X);