MATLAB: How to solve (find zero) of nonanalitical function fzero or fsolve

fzerosolve zero

I have a vector y(x) that does not necessarily have point on y = 0 axis (and is not analytical function).
How can I solve (find the zero crossing) without fitting.
For example:
y = [-1 -0.3 -4 -0.1 0.25 0.4 0.2 0.9  ]
x = [0 0.1 0.2 0.3 0.4 0.5 0.6 0.7]
I would like to solve for y(x)=0

Best Answer

This works:
y = [-1 -0.3 -4 -0.1 0.25 0.4 0.2 0.9];
x = [0 0.1 0.2 0.3 0.4 0.5 0.6 0.7];
yx = find(y>0,1,'first');                   % Choose 1st ‘y’ Point >0
y0 = 0;
x0 = interp1(y(yx-1:yx),x(yx-1:yx),y0);     % Find Zero Cross Between Bracket Points
figure(1)
plot(x, y)
hold on
plot(x0, y0, 'bp')
hold off
grid
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