how to find X-intercept

Hello I am plotting X vs Y and would like to know what is the value of X when Y is equal to zero. I think it is the x intercept. the graph is not really simple its like a wave and I would like to know the first x intercept only. thanks

Answer 1

[Star Strider]

Something like this will do what you want:

x = linspace(0, 10, 250);                                               % Create Data
y = cos(2*pi*x) + x/5;                                              `   % Create Data

zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector

y_idx = zci(y);                                                         % Approximate Indices Of Zero-Crossings
idx_rng = y_idx(1)-1:y_idx(1)+1;                                        % Index Range Near First Zero-Crossing
first_zero = interp1(y(idx_rng),  x(idx_rng), 0, 'linear','extrap');    % Interpolate To Find ‘x’ Of First Zero Crossing, Allow For Extrapolation If Necessary

figure(1)
plot(x, y)
hold on
plot(first_zero, 0, 'gp', 'MarkerSize',10, 'MarkerFaceColor','g')
hold off
grid

[aryan abedi]

I used the same code but I got an error. I was wondering if you could help me please. I know I have to zero crossing analysis but I have no idea how to.