Comparison two curves (functions)

If the function g(z) gives the curve as shown in the figure how can I detect the fault tracepoint (green dash line) and its location on the x-axis as and put a slant line at the curve by Matlab

using the inverting point of the curve? please urgently I need an answer. Thanks in advance.

[dpb]

The figure looks like they found the zero-crossing of the model

Answer 1

[Star Strider]

Use interp1 —

x = linspace(1, 20, 30);
y = tanh(x-12-rand)*2.5;

x0 = interp1(y,x,0)

x0 = 12.7191

figure
plot(x,y, x0,0,'+r', 'MarkerSize',15)
grid
ylim([-3 3])

.