Try this:
t = linspace(0, 5, 500).^3; % Time Vector
s = sin(2*pi*t*0.2); % 10 Hz Sine Curve
zx = find(diff(sign(s))); % Zero-Crossing Indices To ‘t’
for k = 1:numel(zx)
idx_rng = max(zx(k)-1, 1):min(zx(k)+1,numel(t));
tzro(k) = interp1(s(idx_rng), t(idx_rng), 0); % Exact Zero Crossings
end
zx_rate = gradient(tzro); % Calculate Rate
figure
yyaxis left
plot(t, s, '-b')
hold on
plot(tzro, zeros(size(tzro)), 'xr')
hold off
yyaxis right
plot(tzro, zx_rate, 'LineWidth',2)
grid
legend('Signal','Zero-Crossings','Zero-Crossing Rate')
axis('tight')
Once you have the zero-crossings, you can do whatever processing on them that you want.
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