This is my code and I want to find the change points of my sign curve, that is all and I want to put points on the graph where it is concave up and concave down. (2 different shapes for concave up and down would be preferred. I just have a simple sine curve with 3 periods and here is the code below. I have found the first and second derivatives. I'm not sure where to go from here. I know have to set it equal to zero and solve for x, any algorithmic help would be appreciated
x = 1:500;X = x;T = 1; Fs = 499;N = T*Fs;t = 0: 1/Fs : T;Fn = 3; % this control the number of cycles/periods
deltax = 0.0020;y_sine_25HZ = sin(Fn*2*pi*t);y = y_sine_25HZ ;drvY = diff(y)/deltax; % one unit shorter than y
drvY = [drvY , drvY(end)]; % making up for the missing point
secondDrvY = diff(drvY)/deltax;
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