You give no data, so I'll need to make some up for an example.
x = linspace(-30,30,500);
y = cumsum((atan(x - 10)/2 + 1));
plot(x,y)
grid on
So a simple enough curve. Can we locate the point where there is a change? As long as the stride between points is constant, then a tool like findchangepts might help.
ipt = findchangepts(y,'Stat','linear')
[x(ipt),y(ipt)]
hold on
plot(x(ipt),y(ipt),'ro')
